Roger J. Porter MD

• Adjunct Professor of Neurology, University of Pennsylvania, Philadelphia
• Adjunct Professor of Pharmacology
• Uniformed Services University of the Health Sciences, Bethesda

https://www.linkedin.com/in/roger-j-porter-md-scd-437737b

The map is based on the idea of linkage gastritis diet ������� best 10 mg prilosec, which means that the closer two genes are to each other on the chromosome gastritis diabetes diet purchase prilosec with amex, the greater the probability that they will be inherited together gastritis pronounce order prilosec 10mg line. By following inheritance patterns diet of gastritis patient buy prilosec 10mg low cost, the relative locations of genes along the chromosome are established gastritis cancer prilosec 10 mg otc. Genetic markers are used to track the inheritance of a nearby gene that has not yet been identified gastritis diet advice nhs buy prilosec australia, but whose approximate location is known. Once such genetic markers are identified, they can be used to understand how genes contribute to the disease and develop better prevention and treatment strategies. Genomics refers to the study of the entire genome of an organism whereas genetics refers to the study of a particular gene. A germ line is the sex cells (eggs and sperm) that are used by sexually reproducing organisms to pass on genes from generation to generation. Egg and sperm cells are called germ cells, in contrast to the other cells of the body that are called somatic cells. Heterozygous refers to having inherited different forms of a particular gene from each parent. A heterozygous genotype stands in contrast to a homozygous genotype, where an individual inherits identical forms of a particular gene from each parent. Homozygous is a genetic condition where an individual inherits the same alleles for a particular gene from both parents. In contrast, fraternal, or dizygotic, twins result from the fertilization of two separate eggs during the same pregnancy. Inherited traits are passed from parent to offspring according to the rules of Mendelian genetics. Most traits are not strictly determined by genes, but rather are influenced by both genes and environment. The closer two genes are to each other on the chromosome, the greater the probability that they will be inherited together. Cytogenetic maps are made using photomicrographs of chromosomes stained to reveal structural variations. Gregor Mendel was an Austrian monk who, in the 19th century, worked out the basic laws of inheritance, even before the term "gene" had been coined. Mendelian inheritance refers to patterns of inheritance that are characteristic of organisms that reproduce sexually. The Austrian monk Gregor Mendel performed thousands of crosses with garden peas at his monastery during the middle of the 19th century. Mendel explained his results by describing two laws of inheritance that introduced the idea of dominant and recessive genes. Germ line mutations occur in the eggs and sperm and can be passed on to offspring, while somatic mutations occur in body cells and are not passed on. Newborn screening is testing performed on newborn babies to detect a wide variety of disorders. Typically, testing is performed on a blood sample obtained from a heel prick when the baby is 2 or 3 days old. In the United States, newborn screening is mandatory for several different genetic disorders, though the exact set of required tests differs from state to state. A pedigree is a genetic representation of a family tree that diagrams the inheritance of a trait or disease though several generations. The pedigree shows the relationships between family members and indicates which individuals express or silently carry the trait in question. Some traits are largely determined by the genotype, while other traits are largely determined by environmental factors. Traits that display a continuous distribution, such as height or skin color, are polygenic. The inheritance of polygenic traits does not show the phenotypic ratios characteristic of Mendelian inheritance, though each of the genes contributing to the trait is inherited as described by Gregor Mendel. Many polygenic traits are also influenced by the environment and are called multifactorial. In humans, the term generally refers to traits that are influenced by genes on the X chromosome. This is because the X chromosome is large and contains many more genes than the smaller Y chromosome. In a sex-linked disease, it is usually males who are affected because they have a single copy of X chromosome that carries the mutation. In females, the effect of the mutation may be masked by the second healthy copy of the X chromosome. Traits can be determined by genes or the environment, or more commonly by interactions between them. In an X-linked or sex linked disease, it is usually males that are affected because they have a single copy of the X chromosome that carries the mutation. Although the methodologic issues discussed are interesting and intriguing, much of the excitement in epidemiology stems from the fact that epidemiologic results should have direct application to problems involving human health. The challenges include deriving valid inferences from the data generated by epidemiologic studies, ensuring appropriate and clear communication of the findings and their interpretations to policy makers and the general public, and dealing with ethical problems that arise because of the close link of epidemiology to human health and to clinical and public health policy. This section discusses the use of epidemiology in evaluating both health services (Chapter 17) and programs for screening and early detection of disease (Chapter 18). These two chapters also address some of the methodologic and conceptual challenges that I commonly arise in both. We then turn to some other issues involved in the application of epidemiology to the development of policy (Chapter 19), including the relationship of epidemiology to prevention, risk assessment, epidemiology in the courts, and the sources and impact of uncertainty. In the final chapter, we address some of the major ethical and professional considerations that arise both in conducting epidemiologic investigations and in utilizing the results of epidemiologic studies to improve the health of the community. Epidemiologic studies are a major approach for enhancing the effectiveness of both clinical care and public health interventions. This excerpt includes all of the basic components of the process of evaluation: baseline data, implementation of the program, evaluation of the program, and implementation of new program activities on the basis of the results of the evaluation. First, we are not given the precise criteria that were used to determine whether or how the program was "good"; we are told only that God saw that it was good (which, in hindsight, may be sufficient). Second, this evaluation exemplifies a frequently observed problem: the program director is assessing his own program. Furthermore, even if the program director administers the program superbly, he or she may not necessarily have the specific skills that are needed to conduct a methodologically rigorous evaluation of the program. Wade Hampton Frost, a leader in epidemiology in the early part of the 20th century, addressed the use of epidemiology in the evaluation of public health programs in a presentation to the American Public Health Association in 1925. Since his capital comes entirely from the public, it is reasonable to expect that he will be prepared to explain to the public his reasons for making each investment, and to give them some estimate of the returns which he expects. However, as to such accounting, the health officer finds himself in a difficult and possibly embarrassing position, for while he may give a fairly exact statement of how much money and effort he has put into each of his several activities, he can rarely if ever give an equally exact or simple accounting of the returns from these investments considered separately and individually. It is due primarily to the character of the dividends from public health endeavor, and the manner in which they are distributed. They are not received in separate installments of a uniform currency, each docketed as to its source and recorded as received; but come irregularly from day to day, distributed to unidentified individuals throughout the community, who are not individually conscious of having received them. They are positive benefits in added life and improved health, but the only record ordinarily kept in morbidity and mortality statistics is the partial and negative record of death and of illness from certain clearly defined types of disease, chiefly the more acute communicable diseases, which constitute only a fraction of the total morbidity. Indeed, it would have been opportune at any time during the past 40 years and, it is to be feared, will be equally needed for 40 years to come. Studies of Process and Outcome Avedis Donabedian is widely regarded as the author of the seminal work on creating a framework of examining health services in relation to the quality of care. He identified three important factors simultaneously at play: (1) structure, (2) process, and (3) outcome. Structure relates to the physical locations where care is provided, the personnel, equipment, and financing. We will restrict our discussion here to the remaining two components, process and outcome. Process means that we decide what constitutes the components of good care, services, or preventive actions. We can then assess a clinic or health care provider, by reviewing relevant records or by direct observation, and determine to what extent the care provided meets established and accepted criteria. For example, in primary care we can determine what percentage of patients have had their blood pressure measured. Second, because process assessments are often based on expert opinion, the criteria used in process evaluations may change over time as expert opinion changes. For example, in the 1940s, the accepted standard of care for premature infants required that such infants be placed in 100% oxygen. However, when research demonstrated that high oxygen concentration played a major role in producing retrolental fibroplasia-a form of blindness in children who had been born prematurely-high concentrations of oxygen were subsequently deemed unacceptable. Outcome denotes whether or not a patient (or a community at large) benefits from the medical care provided. Although such measures have traditionally been mortality and morbidity, interest in outcomes research in recent years has expanded the measures of interest to include patient satisfaction, quality of life, degree of dependence and disability, and similar measures. For example, when a vaccine is tested in a community, many individuals may not come in to be vaccinated. Or, an oral medication may have such an undesirable taste that no one will take it (so that it will prove ineffective), despite the fact that under controlled conditions, when compliance was ensured, the drug was shown to be efficacious. Cost includes not only money, but also discomfort, pain, absenteeism, disability, and social stigma. If a health care measure has not been demonstrated to be effective, there is little point looking at efficiency, for if it is not effective, the least expensive alternative is not to use it at all. However, this chapter will focus only on the science of evaluation and specifically on the issue of effectiveness in evaluating health services. Efficacy, Effectiveness, and Efficiency Three terms that are often encountered in the literature dealing with evaluation of health services are efficacy, effectiveness, and efficiency. These terms are often used in association with the findings from randomized trials. We test a new drug in a group of patients who have agreed to be hospitalized and who are observed as they take their therapy. Thus, efficacy is a measure in a situation in which all conditions are controlled to maximize the effect of the agent. Generally, "ideal" conditions are those that occur in testing a new agent of intervention using a randomized trial. Measures of Outcome If efficacy of a measure has been demonstrated-that is, if the methods of prevention and intervention that are of interest have been shown to work-we can then turn to evaluating effectiveness. What guidelines should we use in selecting an appropriate outcome measure to serve as an index of effectiveness First, the measure must be clearly quantifiable; that is, we must be able to express its effect in quantitative terms. If the measure is to be used in a population study, we would certainly not want to depend on an invasive procedure for assessing any benefits. Third, the measure selected should lend itself to standardization for study purposes. Fourth, the population served (and the comparison population) must be at risk for the same condition for which an intervention is being evaluated. The type of health outcome end point that we select clearly should depend on the question that we are asking. Whatever outcome we select should be explicitly stated so that others reading the report of our findings will be able to make their own judgments regarding the appropriateness of the measure selected and the quality of the data. Whether the measure we have selected is indeed an appropriate one depends on clinical and public health aspects of the disease or health condition in question. Measures of volume of services provided, numbers of cultures taken, and number of clinic visits have been traditionally used because they are relatively easy to count and are helpful in justifying requests for budgetary increases for the program in the following year. However, such measures are all process measures and tell us nothing about the effectiveness of an intervention. Comparing Epidemiologic Studies of Disease Etiology and Epidemiologic Research Evaluating Effectiveness of Health Services In classic epidemiologic studies of disease etiology, we examine the possible relationship between a putative cause (the independent variable or "exposure") and an adverse health effect or effects (the dependent variable or "outcome"). In health services research, we focus on the health service as the independent variable (the "exposure"), with a reduction in adverse health effects as the anticipated outcome (dependent variable) if the modality of care is effective. Thus, both etiologic epidemiologic research and health services research address the possible relationship between an independent variable and a dependent variable, and the influence of other factors on the relationship. Therefore, it is not surprising that many of the study designs discussed are common to both epidemiologic and health services research, as are the methodologic problems and potential biases that may characterize these types of studies. Number (or proportion) of people immunized and later exposed in whom clinical disease does not develop 5. Number (or proportion) of persons with positive cultures for whom medical care is obtained 4. Number (or proportion) of persons with positive cultures for whom proper treatment is prescribed and taken 5. Evaluation Using Group Data Regularly available data, such as mortality data and hospitalization data, are often used in evaluation studies. Such data can be obtained from different sources, and such sources may differ in important ways. This is potentially attributed to the varying methodology of data collection of each data source. The health end points may include morbidity and mortality as well as measures of quality of life, functional status, and patient perceptions of their health status, including symptom recognition and patient-reported satisfaction. Economic measures may reflect direct or indirect costs, and can include hospitalization rates, rehospitalization for the same condition within 30 days of discharge, outpatient and emergency room visits, lost days of work, child care, and days of restricted activity. Consequently, epidemiology is one of several disciplines needed in outcomes research.

The problem with selecting simultaneous controls in a nonrandomized manner is illustrated by the following story: A sea captain was given samples of anti-nausea pills to test during a voyage gastritis diet ketosis discount 10mg prilosec otc. One is to assign patients by the day of the month on which the patient is admitted to the hospital: for example gastritis diet mayo clinic 10 mg prilosec free shipping, if admission is on an odd-numbered day of the month the patient is in group A gastritis lipase purchase prilosec 40mg with mastercard, and if admission is on an even-numbered day of the month the patient 10 Assessing Preventive and Therapeutic Measures: Randomized Trials 201 is in group B gastritis diet 411 best buy prilosec. The investigators reported that "as physicians observed the benefits of anticoagulant therapy gastritis define generic prilosec 10mg, they speeded up gastritis treatment dogs prilosec 10mg on line, where feasible, the hospitalization of those patients. The goal of randomization is to eliminate the possibility that the investigator will know what the assignment of the next patient will be, because such knowledge introduces the possibility of bias on the part of the investigator regarding the treatment group to which each participant will be assigned. However, as the investigators wrote: Subsequent experience has shown that by this method of selection, the tendency was to inoculate the children of the more intelligent and cooperative parents and to keep the children of the noncooperative parents as controls. This was probably of considerable error since the cooperative parent will not only keep more careful precautions, but will usually bring the child more regularly to the clinic for instruction as to child care and feeding. To address this problem, a change was made in the study design: alternate children were vaccinated and the remainder served as controls. This does not constitute randomization, but it was a marked improvement over the initial design. Allocating Subjects Using Randomization In view of the problems discussed, randomization is the best approach in the design of a trial. Randomization means, in effect, tossing a coin to decide the assignment of a patient to a study group. The critical element of randomization is the unpredictability of the next assignment. Although random allocation is currently usually done through computer programs, on occasion manual randomization is used either as a backup to computer-generation assignment or when access to a computer is limited. Note that the table is divided into 10 rows and 4 numbered columns (row numbers appear on the far left columns). This means that the number in Column 00 is 5, the number in Column 01 is 6, the number in Column 03 is 3, etc. Thus it is possible to refer to any digit in the table by giving its column and row numbers. This is important if the quality of the randomization process is to be checked by an outsider. Let us say that we are conducting a study in which there will be two groups: therapy A and therapy B. In this example, we will consider every odd number an assignment to A and every even number an assignment to B. We close our eyes and put a finger anywhere on the table, and write down the column and row number that was our starting point. We also write down the direction we will move in the table from that starting point (horizontally to the right, horizontally to the left, up, or down). Let us assume that we point to the "5" at the intersection of column 07 and row 07 and move horizontally to the right. The first patient, then, is designated by an odd number, 5, and will receive therapy A. The second patient is also designated by an odd number, 3, and will receive therapy A. The third is designated by an even number, 8, and will receive therapy B, and so on. Note that the next patient assignment is not predictable; it is not a strict alternation, which would be predictable and hence subject to investigator bias, knowingly or unknowingly. There are many ways of using a table of random numbers for allocating patients to treatment groups in a randomized trial (Box 10. Although many approaches are valid, the important point is to spell out in writing whatever approach is selected for use, before randomization is actually begun. Having decided conceptually how to use the random numbers for allocating patients, how do we make a practical decision as to which patients get which 10 Assessing Preventive and Therapeutic Measures: Randomized Trials 203 therapy Let us assume, for example, that a decision has been made that odd digits will designate assignment to treatment A and even digits will designate treatment B. The treatment assignment that is designated by the random number is written on a card, and this card is placed inside an opaque envelope. Each envelope is labeled on the outside: Patient 1, Patient 2, Patient 3, and so on, to match the sequence in which the patients are enrolled in the study. For example, if the first random number is 2, a card for therapy B would be placed in the first envelope; if the next random number is 7, a card for therapy A in the second one, and so on, as determined by the random numbers. When the first patient is enrolled, envelope 1 is opened and the assignment is read; this process is repeated for each of the remaining patients in the study. The following anecdote illustrates the need for careful quality control of any randomized study: In a randomized study comparing radical and simple mastectomy for breast cancer, one of the surgeons participating was convinced that radical mastectomy was the treatment of choice and could not reconcile himself to performing simple mastectomy on any of his patients who were included in the study. When randomization was carried out for his patients and an envelope was opened that indicated simple mastectomy for the next assignment, he would set the envelope aside and keep opening envelopes until he reached one with an assignment to radical mastectomy. What is reflected here is the conflict experienced by many clinicians who enroll their own patients in randomized trials. On the one hand, the clinician has the obligation to do the best he or she can for the patient; on the other hand, when a clinician participates in a clinical trial, he or she is, in effect, asked to step aside from the usual decision-making role and essentially to "flip a coin" to decide which therapy the patient will receive. This is such a common problem, particularly in large, multicentered trials, that randomization is not carried out by each participating clinical field center; rather, it is done by an impartial separate coordinating and statistical center. When a new patient is registered at a clinical center, the coordinating center is called or an assignment is downloaded by the coordinating center. A randomized assignment is then made for that patient by the coordinating center, and the assignment is noted in both the clinical and centralized locations. If we randomize properly, we achieve nonpredictability of the next assignment; we do not have to worry that any subjective biases of the investigators, either overt or covert, may be introduced into the process of selecting patients for one treatment group or the other. In addition, if the study is large enough and there are enough participants, we hope that randomization will increase the likelihood that the groups will be comparable to each other in regard to characteristics about which we may be concerned, such as sex, age, race, and severity of disease-all factors that may affect prognosis. Randomization is not a guarantee of comparability because chance may play a role in the process of random treatment assignment. However, if the treatment groups that are being randomized are large enough and the randomization procedure is free of bias, they will tend to be similar. Let us assume a study population of 2,000 subjects with myocardial infarctions, of whom half receive an intervention and the other half do not. Let us further assume that of the 2,000 patients, 700 have an arrhythmia and 1,300 do not. Case-fatality in patients with the arrhythmia is 50%, and in patients without the arrhythmia it is 10%. Because there is no randomization, the intervention groups may not be comparable in the proportion of patients who have the arrhythmia. Perhaps 200 in the intervention group may have the arrhythmia (with a case-fatality of 50%) and 500 in the no-intervention group may have the arrhythmia (with its 50% case-fatality). The resulting case-fatality will be 18% in the intervention group and 30% in the no-intervention group. I, If the study is not randomized, the proportions of patients with arrhythmia in the two intervention groups may differ. In this example, individuals with arrhythmia are less likely to receive the intervention than individuals without arrhythmia. As seen here, the groups are comparable, as is likely to occur when we randomize, so that 350 of the 1,000 patients in the intervention group and 350 of the 1,000 patients in the nointervention group have the arrhythmia. Thus the difference observed between intervention and no intervention when the groups were not comparable in terms of the arrhythmia was entirely due to the noncomparability and not to any effects of the intervention itself. The answer is that we can match only on variables that we know about and that we can measure. In addition, if we match on a particular characteristic, we cannot analyze its association with the outcome because the two groups will already be identical. However, at the end of the day, randomization cannot always guarantee comparability of the groups being studied. We can analyze whether there are important differences between the two groups that may be associated with the trial outcome. The main purpose of randomization is to prevent any potential biases on the part of the investigators from influencing the assignment of participants to different treatment groups. When participants are randomly assigned to different treatment groups, all decisions on treatment assignment are removed from the control of the investigators. Thus the use of randomization is crucial to protect the study from any biases that might be introduced consciously or subconsciously by the investigator into the assignment process. As mentioned previously, although randomization often increases the comparability of the different treatment groups, randomization does not guarantee comparability. Another benefit of randomization is that to whatever extent it contributes to comparability, this contribution applies both to variables we can measure and to variables that we cannot measure and may not even be aware of, even though they may be important in interpreting the findings of the trial. Stratified Randomization Sometimes we may be particularly concerned about comparability of the groups in terms of one or a few important characteristics that we strongly think may influence prognosis or response to therapy in the groups being studied, but as we have just said, randomization does not ensure comparability. An option that can be used is stratified randomization, an assignment method that can be very helpful in increasing the likelihood of comparability of the study groups. In this section, we will show how this method is used to assign participants to different study groups. For example, let us say that we are particularly concerned about age as a prognostic variable: prognosis is much worse in older patients than among the younger. Therefore we are concerned that the two treatment groups be comparable in terms of age. Although one of the benefits of randomization is that it may increase the likelihood of such comparability, it does not guarantee it. It is still possible that after we randomize, we may, by chance, find that most of the older patients are in one group and most of the younger patients are in the other. Our results would then be impossible to interpret because the higher-risk patients would be clustered in one group and the lower-risk patients in the other. Any difference in outcome between intervention groups may then be attributable to this difference in the age distributions of the two groups rather than to the effects of the intervention. In stratified randomization, we first stratify (stratum = layer) our study population by each variable that we consider important and then randomize participants to treatment groups within each stratum. We are studying 1,000 patients and are concerned that sex and age are important determinants of prognosis. If we randomize, we do not know what the composition of the groups may be in terms of sex and age; therefore we decide to use stratified randomization. We now have four groups (strata): younger males, older males, younger females, and older females. We now randomize within each group (stratum), and the result is a new treatment group and a current treatment group for each of the four groups. As in randomization without stratification, we end up with two intervention groups, but having initially stratified the groups, we increase the likelihood that the two groups will be comparable in terms of sex and age. Let us consider some of the variables about which data need to be obtained on the subjects. It is important to know, for example, if the patient was assigned to receive treatment A but did not comply. A patient may agree to be randomized but may later change his or her mind and refuse to comply. Conversely, it is also clearly important to know whether a patient who was not assigned to receive treatment A may have taken treatment A on his or her own, often without the investigators knowing. Such measurements include both improvement (the desired effect) and any side effects that may appear. There is therefore a need for explicitly stated criteria for all outcomes to be measured in a study. Once the criteria are explicitly stated, we must be certain that they are measured comparably in all study groups. In particular, the potential pitfall of outcomes being measured more carefully in those receiving a new drug than in those receiving currently available therapy must be avoided. Blinding (masking), discussed later, can prevent much of this problem, but because blinding is not always possible, attention must be given to ensuring comparability of measurements and of data quality in all of the study groups. All-Cause Mortality Outcome ("Public Health Outcome") On occasion a medication or a preventive strategy for mortality that is effective with regard to the main outcome of interest does not increase event-free survival. For example, in the 13-year follow-up of the European Randomized Study of Screening for Prostate Cancer, there was a reduction of approximately 27% in prostate cancer mortality. For example, if age is a significant risk factor, we would want to know that randomization has resulted in groups that are comparable for age. Data for prognostic factors should be obtained at the time of subject entry into the study, and then the two (or 10 Assessing Preventive and Therapeutic Measures: Randomized Trials 207 more) groups can be compared on these factors at baseline. Another strategy to evaluate comparability is to examine an outcome totally unrelated to the treatment that is being evaluated. This is of particular importance when the outcome is a subjective measure, such as self-reported severity of headache or low back pain. If the patient knows that he or she is receiving a new therapy, enthusiasm and certain psychological factors on the part of the patient may operate to elicit a positive response even if the therapy itself had no positive biologic or clinical effect. One way is by using a placebo, an inert substance that looks, tastes, and smells like the active agent. However, use of a placebo does not automatically guarantee that the patients are masked (blinded). Some participants may try to determine whether they are taking the placebo or active drug. For example, in a randomized trial of vitamin C for the common cold, patients were blinded by use of a placebo and were then asked whether they knew or suspected which drug they were taking. The data suggest that the rate of colds was higher in subjects who received vitamin C but thought they were receiving placebo than in subjects who received placebo but thought they were receiving vitamin C. Thus we must be very concerned about lack of masking or blinding of the subjects and its potential effects on the results of the study, particularly when we are dealing with subjective end points.

Furthermore can gastritis symptoms come go buy cheap prilosec 20mg on line, some surgeons advocate for preoperative bowel preparation chronic gastritis/lymphoid hyperplasia buy prilosec in united states online, including enema gastritis young living cheap prilosec on line, to help decompress the bowel gastritis translation purchase prilosec overnight, theoretically decreasing the rate of bowel injury gastritis reflux discount prilosec 20 mg line. A nasogastric tube can also be placed preoperatively to facilitate bowel decompression gastritis quotes buy prilosec overnight delivery. Violation of the peritoneum during the retroperitoneal approach or violation of the transversalis fascia during iliac bone graft harvest can lead to the development of postoperative hernias. Although hernias occur in less than 1% of cases, they can lead to bowel obstruction and/or infaction. Graft absorption may also occur, especially in smokers, although this complication is rare. The aforementioned complication may be minimized by the addition of anterior or posterior instrumentation. Furthermore, if a unilateral approach is used, the contralateral lamina, facet joint, and pars can be spared, which provides increased surface area for fusion. Higher rates of nonunion are seen in patients who smoke more than one pack of cigarettes daily. Two years following multilevel fusion for scoliosis, this patient presented with increasing back pain. In most cases, the paresthesias improve within 4 to 12 weeks postoperatively, with more than 90% recovering by 1 year. However, this was not a statistically significant difference, possibly owing to low sample size. Most cases of weakness, numbness, or paresthesias are usually resolved by six months postoperatively. Furthermore, dilation should not be greater than the minimum required for diskectomy. Lastly, less "breaking of the table" has been theorized to decrease the incidence of ipsilateral lumbar plexus injury. Originally, ipsilateral hip flexor/knee extensor weakness, numbness, and/or pain was thought to be caused by dissection through the psoas muscle; however, it is currently thought more likely to be caused by stretching the lumbar plexus during positioning. For all interbody fusions, care must be taken in patients with advanced osteoporosis. Surgery may be indicated for discitis, which fails to be effectively treated with antibiotics. In this situation, diskectomy may be required to effectively debride the disk space. Conclusion Interbody fusion is effective for successful treatment of a number of lumbar pathologies. A number of complications may be seen following each specific interbody technique. These complications may be mitigated by careful patient selection and careful attention to detail. Allograft implants for posterior lumbar interbody fusion: results comparing cylindrical dowels and impacted wedges. Complications of posterior lumbar interbody fusion when using a titanium threaded cage device. Incidence, etiology, classification, and management of neuralgia after posterior lumbar interbody fusion surgery in 226 patients. Surgical complications of posterior lumbar interbody fusion with total facetectomy in 251 patients. A comparison of posterior lumbar interbody fusion and transforaminal lumbar interbody fusion: a literature review and meta-analysis. Preventive effect of artificial ligamentous stabilization on the upper adjacent segment impairment following posterior lumbar interbody fusion. Clinical outcomes of 3 fusion methods through the posterior approach in the lumbar spine. These grafts may be secured in the interbody space via a lateral plate, screw rod construct, or integrated screw plate design. Alternatively, they may be secured via posterior pedicle, facet screws, or spinous process plate. If this does occur, the graft must be removed via open or direct lateral approach. Rodgers and colleagues38 also described one incidence of gastric volvulus in their series of 600 patients. Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004. Visceral and vascular complications resulting from anterior lumbar interbody fusion. Mini-open approach to the spine for anterior lumbar interbody fusion: description of the procedure, results and complications. Occlusion of the left common iliac artery and consecutive thromboembolism of the left popliteal artery following anterior lumbar interbody fusion. Perioperative complications in transforaminal lumbar interbody fusion versus anterior-posterior reconstruction for lumbar disc degeneration and instability. Eur Spine J Off Publ Eur Spine Soc Eur Spinal Deform Soc Eur Sect Cerv Spine Res Soc. Acute contralateral radiculopathy after unilateral transforaminal lumbar interbody fusion. Posterior migration of fusion cages in degenerative lumbar disease treated with transforaminal lumbar interbody fusion: a report of three patients. Clinical and radiological outcomes of minimally invasive versus open transforaminal lumbar interbody fusion. Clinical and radiographic comparison of mini-open transforaminal lumbar interbody fusion with open transforaminal lumbar interbody fusion in 42 patients with long-term follow-up. An analysis of postoperative thigh symptoms after minimally invasive transpsoas lumbar interbody fusion. Minimally invasive lateral lumbar interbody fusion and transpsoas approach-related morbidity. Substantial clinical benefit of minimally invasive lateral interbody fusion for degenerative spondylolisthesis. Each lumbar vertebra is an anatomically complex structure that consists of multiple distinct subunits. Adjacent vertebrae are connected through the disk space anteriorly and the paired zygapophyseal (facet) joints posteriorly. The lumbar spinal canal houses the conus medullaris rostrally, along with the emerging cauda equina, with each lumbar nerve root extending caudally and exiting the canal through its neural foramen directly below the same-numbered pedicle. Understanding the anatomic relationships between these neural structures and the neighboring vertebral bone, disk, and ligament is key to performing effective and safe posterior interbody fusion. The most ventral part of each vertebra is the vertebral body, a cylindrically shaped unit that serves to support axial loads. In the lumbar spine, where the bodies are largest, the average vertebral body height is 27 mm and is similar among all lumbar levels. In the axial plane, the anterior-posterior length is greater than the transverse width, and the bodies are longer and wider at either endplate than at their cranial-caudal midpoint. The transverse width and mid-sagittal length of the vertebral bodies increase progressively from L1 (29 mm wide and 40 mm long at the cranial-caudal midpoint) to L5 (32 mm wide and 46 mm long). Its central portion is thinnest and porous, whereas the outer portion (the apophyseal ring) is thicker and stronger. Each pedicle is angled medially in the axial plane from posterior to anterior, and this angle increases progressively from L1 (average medial angulation of 11 degrees) to L5 (30 degrees). The sagittal pedicle height displays an opposite relationship, decreasing slightly from L1 (15. The lamina is a sheet-like subunit that forms the dorsal roof of the spinal canal. In the sagittal plane, it slopes posteriorly from superior to inferior; in the axial plane, it is angled posteriorly from lateral to medial, with an apex at the midline. When viewed in the coronal plane, the lamina is tall and narrow at the superior lumbar levels and becomes shorter and wider as it goes down to the lower lumbar levels. The spinous process is oriented in the midline sagittal plane and projects dorsally from the lamina with downward angulation, lying slightly below its corresponding vertebral body and overlying the subjacent interlaminar space. The spinous process is the most dorsal part of the vertebra and the first bone encountered during posterior midline surgical exposure. The zygapophyseal (facet) joints are paired synovial joints that allow for articulation of the posterior portion of the vertebrae. Each of the apposed articular surfaces consists of smooth cortical bone covered with a layer of hyaline cartilage. The joint space contains synovial fluid and is enclosed posteriorly by a fibrous capsule. This orientation allows significant flexion/extension and moderate lateral bending, but minimal axial rotation. The ligamentum flavum has its origin on the superior dorsal edge of the caudal lamina and inserts onto the inferior ventral edge of the superior lamina. The ligamentum flavum is surgically relevant because it is often hypertrophied in the degenerative spine, in which case it can cause compression of the central canal and lateral recess, and removal of this compressive ligament is key to an effective decompressive surgery. During laminectomy, the ligamentum protects the dura from violation during exposure and bone removal. Because of its discontinuity, the upper half of the lamina has no ligamentum ventrally between the bone and dura, a crucial anatomic landmark in tubular surgical procedures. The surgeon must also be aware that in patients who have undergone previous operations, the ligamentum flavum may be absent at a given level, a point of caution in reexploratory surgeries where inadvertent dural tears may occur. The lumbar interspinous ligament is discontinuous and spans the interval between spinous processes in the sagittal plane, whereas the supraspinous ligament is a continuous structure that runs in the midline along the dorsal edge of the spinous process; both provide resistance to flexion. The intervertebral disk allows for transmission of axial loads between vertebral bodies while permitting motion at each segment. Removal of ectopic disk material is therefore a principal component of many surgical interventions. There are 23 disks in the typical spine, one at each level from C2-3 through L5-S1, and these disk spaces are relevant to interbody fusion, as they serve as the site of arthrodesis. In this setting, it is important to perform a thorough diskectomy including removal of the cartilaginous endplates, to allow for sufficient exposure of the bony endplate and placement of ample bone graft to create optimal conditions for fusion. The sacrum deserves brief mention because it articulates with the lumbar spine and is often instrumented in the setting of lumbar fusion. The rostral laminae are fused, with no interlaminar space, and the median sacral crest represents the fused former spinous processes. The posterior neuroforamina are arranged in paired vertical rows on each side and are the sites of exit of the dorsal rami from the spinal canal. S1 varies from the lumbar vertebrae in that the body and pedicles are flanked on each side by large alae. This means that S1 pedicle screws tend to be shorter and have less cortical bone surrounding them, making them more susceptible to pullout or toggling. Strategies for optimizing pullout strength given these limitations include bicortical purchase through the ventral S1 cortex, or tricortical purchase by directing the screw to the apex of the sacral promontory. Iliac screws or additional points of sacral fixation may be helpful in this scenario. The posterior edges of the canal meet at an apex in the midline, and are formed by the lamina and facet on each side, and the underlying ligamentum flavum. The height remains relatively constant among levels in the lumbar spine (17 mm), whereas the width increases progressively from L1 (22 mm) to L5 (26 mm). The venous plexus must often be coagulated in order to access the disk space and to retract the thecal sac and nerve root medially. The neural foramen serves as the exit site for the nerve root and is frequently the site of symptomatic compression from degenerative pathology. The upper portion is bordered anteriorly by the vertebral body and superiorly by the pedicle of the same numbered vertebra. The inferior portion of the foramen is bordered anteriorly by the disk and inferiorly by the pedicle of the subjacent vertebra. The important neural structures of the lumbar spine include the lower spinal cord, conus medullaris, and nerve roots. In normal adults, the conus terminates at the L1 level on average, with a range of T12 to L2/3,18 but in pathologic conditions it can lie much lower. Below the conus, the nerve roots of the more caudal levels form the cauda equina and travel caudally within the spinal canal. As a root nears its same-numbered vertebral level, it courses laterally into the lateral recess and exits the dura at or just below the superjacent disk space. The extradural nerve root then travels in an inferolateral direction and exits the spinal canal just below the same-numbered pedicle. Unlike posterolateral fusion, it is not necessary to expose the lateral aspects of the facet joints and the transverse processes when performing interbody fusion. The disk space lies deep to the inferior articulating process (or superior half of the facet joint) and the inferior edge of the lamina. The neural foramen lies deep to the pars, and the exiting nerve root passes through the superior portion of the foramen, just below the pedicle, as it travels laterally. The dashed lines toward the left of the spine represent the projections of deeper structures, including the samenumbered pedicle (P), exiting nerve root (R), intervertebral disk (D), subjacent pedicle (P), and traversing nerve root (R). The spinal elements of the index level have been outlined and labeled for easier visualization. The lamina (L) slopes downward where it meets the pars interarticularis (arrow) and the facet joint capsules (F). The posterolateral aspect of the intervertebral disk (arrow) is seen ventral to the thecal sac and nerve root. This window, which serves as the site of entry into the disk space, is bordered medially by the thecal sac and traversing nerve root, inferiorly by the pedicle of the vertebra below, and superolaterally by the exiting nerve root (not well visualized in this photograph).

Important considerations in investigating an acute outbreak of infectious diseases include determining that an outbreak has in fact occurred and defining the extent of the population at risk gastritis quizlet buy prilosec visa, determining the measure of spread and reservoir gastritis blog order prilosec now, and characterizing the agent gastritis bile purchase prilosec. Steps commonly used are listed below symptoms of gastritis in cats order prilosec uk, but depending on the outbreak gastritis diet ultimo purchase 20mg prilosec with amex, the exact order may differ nodular gastritis definition buy 20 mg prilosec fast delivery. Define the "denominator": What is the population at risk of developing disease. Determine whether the observed number of cases clearly exceeds the expected number d. Communicate findings to those involved in policy development and implementation and to the public a very helpful method for determining which of the possible agents is suspected to be the cause is called cross-tabulation. On a questionnaire administered to 185 randomly selected inmates, 47% reported a sore throat between August 16 and August 22. Based on a second questionnaire, food-specific attack rates for items that were served to randomly selected inmates showed an association between two food items and the risk of developing a sore throat: a beverage and an egg salad served at lunch on August 16 (Table 2. For both the beverage and the egg salad, attack rates are clearly higher among those who ate or drank the item than among those who did not. However, this table does not permit us to determine whether the beverage or the egg salad accounted for the outbreak. Looking at the data by columns, we see that both among those who ate egg salad and among those who did not, drinking the beverage did not increase the incidence of streptococcal illness (75. However, looking at the data in the table rows, we see that eating the egg salad increased the attack rate of the illness, both in those who drank the beverage (75. Further discussion of the analysis and interpretation of cross-tabulation can be found in Chapter 15. This example demonstrates the use of cross-tabulation in a food-borne outbreak of an infectious disease, but the method has broad applicability to any condition in which multiple etiologic factors are suspected. An example is a cruise-ship outbreak of gastrointestinal illness that occurred on the same day as a rainstorm, resulting in billions of liters of storm runoff being contaminated with sewage that had been released on the lake where the cruise took place. The cross-tabulation showed that passengers consuming ice had an attack rate more than twice as high as the rate among those who did not consume ice. Stool specimens were positive for multiple agents, including Shigella sonnei and Giardia. Many of these concepts apply equally well to noncommunicable diseases that at this time do not appear to be primarily infectious in origin. Moreover, for an increasing number of chronic diseases originally thought to be noninfectious, infection seems to play some role. Papillomaviruses and Helicobacter 2 the Dynamics of Disease Transmission 39 pylori infections are necessary for the development of cervical and gastric cancers, respectively. The boundary between the epidemiology of infectious and noninfectious diseases has blurred in many areas. In addition, even for diseases that are not infectious in origin, inflammation may be involved, the patterns of spread share many of the same dynamics, and the methodologic issues in studying them are similar. Hearing on ensuring kidney patients receive safe and appropriate anemia management care. House of Representatives, 110th Congress, First Session, June 26, 2007, Serial No. Outbreaks of gastroenteritis associated with noroviruses on cruise ships-United States, 2002. Observations Made During the Epidemic of Measles on the Faroe Islands in the Year 1846. New York: Delta Omega Society, Distributed by the American Public Health Association; 1940. Multi-pathogen water, borne disease outbreak associated with a dinner cruise on Lake Michigan. Is prevalent among animals Questions 2 and 3 are based on the information given below: the first table shows the total number of persons who ate each of two specified food items that were possibly infective with group A streptococci. The second table shows the number of sick persons (with acute sore throat) who ate each of the various specified combinations of the food items. Neither tuna nor egg salad 4 In the study of an outbreak of an infectious disease, plotting an epidemic curve is useful because: a. All of the above 6 Which of the following recent widespread disease is considered pandemic Disease Surveillance and Measures of Morbidity We owe all the great advances in knowledge to those who endeavor to find out how much there is of anything. If you can measure that of which you speak, and can express it by a number, you know something of your subject, but if you cannot measure it, your knowledge is meager and unsatisfactory. Much of our information about morbidity and mortality from disease comes from programs of systematic disease surveillance. Surveillance was commonly conducted for infectious diseases, but in recent years it has become increasingly important in monitoring changes in other types of conditions such as congenital malformations, noncommunicable diseases, and environmental toxins, and for injuries and illnesses after natural disasters such as hurricanes or earthquakes. It is clear from that discussion that in order to examine the transmission of disease in human populations, we need to be able to measure the frequency of both disease occurrence and deaths from the disease. In this article, we will describe disease surveillance in human populations and its importance in providing information about morbidity from disease. In order to enable countries or states to develop coordinated public health approaches, mechanisms for information exchange are essential. Consequently, standardized case definitions of disease and diagnostic criteria are needed that can be applied in different countries or for the purpose of public health surveillance within a country. The forms used for collecting and reporting data on different diseases must also be standardized. The completeness and quality of the data reported thus largely depend on this individual and his or her staff, who often take on this role without additional funds or resources. As a result, underreporting and lack of completeness of reporting are likely; to minimize this problem, the reporting instruments must be simple and brief. When passive reporting is used, local outbreaks may be missed because the relatively small number of cases often ascertained becomes diluted within a large denominator of a total population of a province or country. However, a passive reporting system is relatively inexpensive and relatively easy to develop initially. Monitoring flu outbreaks by assessing Google searches or social media are examples of how this may take place in communities. In addition, as many countries have systems of passive reporting for a number of reportable diseases that are generally infectious, passive reporting allows for international comparisons that can identify areas that urgently need assistance in confirming new cases and in providing appropriate interventions for control and treatment. Active surveillance denotes a system in which project staff are specifically recruited to carry out a surveillance program. They are recruited to make periodic field visits to health care facilities such as clinics, primary health care centers, and hospitals in order to identify new cases of a disease or diseases or deaths from the disease that have occurred (case finding). Active surveillance may involve interviewing physicians and patients, reviewing medical records, and, in developing countries and rural areas, surveying villages and towns to detect cases either periodically on a routine basis or after an index case has been reported. Reporting is generally more accurate when surveillance is active than when it is passive because active surveillance is conducted by individuals who have been specifically employed and trained to carry out this responsibility. When passive surveillance is used, existing staff members (commonly physicians) are often asked to report new cases. However, they are often overburdened by their primary responsibilities of providing health care and administering health services. For them, filing reports of new cases is an additional burden that they often view as peripheral to their main responsibilities. Furthermore, with active reporting, local outbreaks are generally more easily identified. But active reporting is more expensive to maintain than passive reporting and is often more difficult to develop initially. For example, areas in need of surveillance may be difficult to reach, and it may be difficult to maintain communication from such areas to the central authorities who must make policy decisions and allocate the resources necessary for follow-up and disease control and prevention. Furthermore, definitions of disease used in developed countries may at times be inappropriate or unusable in developing countries because of a lack of the laboratory and other sophisticated resources needed for full diagnostic evaluation of suspected cases. Disease Surveillance and Measures of Morbidity 43 2014 West Africa Ebola outbreak and the 2015 Zika virus epidemic in Latin America and the Caribbean. One example of the challenges in disease surveillance using mortality data is the problem of differing estimates of mortality from malaria, one of the major killers today, especially in poor, developing countries. Since then, deaths due to malaria have decreased substantially, particularly in sub-Saharan Africa. This has been attributed to the successful expansion of vector control activities, such as insecticide-treated bed nets to prevent infection and improved treatment of those already infected. Surveillance may also be carried out to assess changes in levels of environmental risk factors for disease. For example, monitoring levels of particulate air pollution or atmospheric radiation may be conducted, particularly after an accident has been reported. A unique example of this is the explosion of the Fukushima Daiichi nuclear power plant in Fukushima, Japan in 2011. Thus surveillance for changes in either disease rates or levels of environmental risk factors may serve as a measure of the severity of the accident and point to possible directions for reducing such hazards in the future. In certain situations, hospitalization may be required, either for diagnosis or for treatment, or for both. One of several outcomes can then result: cure, control of the disease, disability, or death. If we want information about the illness before medical care was sought, we may obtain this information from the patient using a questionnaire or an interview. Not shown in this figure are the records of health insurers, which at times can provide very useful information. The source of data from which cases are identified clearly influences the rates that we calculate for expressing the frequency of disease. Consequently, when we see rates for the frequency of occurrence of a certain disease, we must identify the sources of the cases and determine how the cases were identified. When we interpret the rates and compare them to rates reported in other populations and at other times, we must take into consideration the characteristics of the sources from which the data were obtained. Rates tell us how fast the disease is occurring in a population; proportions tell us what fraction of the population is affected. Let us turn to how we use rates and proportions for expressing the extent of disease in a community or other population. In this article, we discuss measures of illness or morbidity; measures of mortality are discussed in Chapter 4. Disease Surveillance and Measures of Morbidity 45 period of time in a population at risk for developing the disease. The choice of 1,000 is more or less arbitrary-we could have used 10,000, 1 million, or any other figure. However, this choice is generally influenced by the frequency of the disease; for example, for a common disease, such as the common cold, incidence is usually defined as a percentage; for rare diseases, such as aplastic anemia, it is multiplied by 100,000 or even 1,000,000. Incidence rate is a measure of events-the disease is identified in a person who develops the disease and did not have the disease previously. This risk can be looked at in any population group, such as a particular age group, among males or females, in an occupational group, or a group that has been exposed to a certain environmental agent, such as radiation or a chemical toxin. However, a problem in interpreting such data is the possibility that the observed increase could be due to more intensive screening that was initiated following the accident. Such screening could have identified thyroid tumors that might otherwise not have been detected and thus might not have been attributed to the common exposure (the reactor). Nevertheless, there is now general agreement that the observed increase in thyroid cancer in children and adolescents in areas exposed to Chernobyl fallout was, in fact, real. The denominator of an incidence rate represents the number of people who are at risk for developing the disease. For an incidence rate to be meaningful, any individual who is included in the denominator must have the potential to become part of the group that is counted in the numerator. Thus, if we are calculating incidence of uterine cancer, the denominator must include only women with no history of hysterectomy, because women with a history of hysterectomy and men would never have the potential to become part of the group that is counted by the numerator, that is, both are not at risk for developing uterine cancer. Although this point seems obvious, it is not always so clear, and we shall return to this issue later in the discussion. Incidence measures can use two types of denominators: people at risk who are observed throughout a defined time period; or, when all people are not observed for the full time period, person-time (or units of time when each person is observed). The choice of time period is arbitrary: We could calculate incidence in 1 week, incidence in 1 month, incidence in 1 year, incidence in 5 years, and so on. The incidence is calculated using a period of time during which all of the individuals in the population are considered to be at risk for the outcome, also called the cumulative incidence proportion, which is a measure of risk. When All People Are Not Observed for the Full Time Period, Person-Time, or Units of Time When Each Person Is Observed Often, every individual in the denominator cannot be followed for the full time specified for a variety of reasons, including loss to follow-up or death from a cause other than that being studied. When different individuals are observed for different lengths of time, we calculate an incidence rate (also called an incidence density), in which the denominator consists of the sum of the units of time that each individual was at risk and was observed. This is called person-time and is often expressed in terms of person-months or person-years (py) of observation. In this diagram, the two arrows represent two people who were observed for all 5 years. The timelines for the three other people end with a red "x," which indicates the point at which the observation of each individual ended, either because the event of interest occurred or because the person was lost to follow-up, or other problems. As a result, only two participants remained and were observed in the fifth year of the study. In certain situations, it may be possible to monitor an entire population over time with tests that can detect newly developed cases of a disease. Those who do not have the disease at baseline are followed for the specified time, such as 1 year. Any cases that are identified clearly developed disease during the 1-year period since those followed were free of disease at the beginning of the year. Thus these cases are new or incident cases and serve as the numerator for the incidence rate. Although in most situations it is necessary to express incidence by specifying a denominator, at times, the number of cases alone may be informative. The number of cases reported in a year in the United States (since reporting began) reached an all-time low in 2015.

Order cheap prilosec on-line. I drank CELERY JUICE for 7 Days and this is what happened....