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BHAGATH M S
RAJEEV BISWAS
LAB 1 QUESTIONS QUESTIONS 1-7: FOR EACH NUMBERED SITUATION BELOW, SELECT THE MOST APPROPRIATE MEASURE FROM THE FOLLOWING LETTERED OPTIONS. EACH LETTERED OPTION CAN BE USED ONCE, MORE THAN ONCE, OR NOT AT ALL. A. Prevalence C. Incidence rate
B. Risk D. Case fatality
E. Median survival 1. Which is the best measure to estimate the rapidity with which new cases of asthma develop among schoolaged children?C 2. Which is the best measure to estimate the proportion of nursing home residents that is clinically depressed?B 3. Which is the best measure to estimate the typical longevity after diagnosis of patients who have experienced a stroke? E 4.Which is the best measure to estimate the likelihood that women who start postmenopausal hormone replacement therapy will develop breast cancer within 10 years? B 5.Which is the best measure to estimate the likelihood of death within 30 days for persons who have experienced an episode of major head trauma? D 6. Which is the best measure to estimate the proportion of persons aged 65 years that has cataracts? A 7. Which is the best measure to estimate the likelihood that employees at a manufacturing plant will experience an episode of lower back pain within a 1-year period of time? B
Questions 8-9: A study about risk of myocardial infarction among cigarette smokers was conducted between 1994 and 1999. The results of observations on six patients are depicted schematically in Figure 2-8.
8. The prevalence of myocardial infarction in 1995 was A. 1/6=0.17 B. 1/5 = 0.20 C. 2/6=0.33 D. 2/5 = 0.40 E. 3/5 = 0.60 9. Among these patients, the risk of developing a myocardial infarction by the end of the second year of followup is A. 1/6 = 0.17 B. 1/5 = 0.20 C. 2/6=0.33 D. 2/5 = 0.40
E. 3/5 = 0.60 Questions 10-11: A survival curve for patients with multiple myoloma is shown in Figure 2-9.
10. From this curve, the median survival is estimated to be between A. 0 and 1 year B. 1 and 2 years C. 2 and 3 years D. 3 and 4 years E. 4 and 5 years 11. From this curve, the 5-year survival is estimated to be closest to A. 30% B. 40% C. 50% D. 60% E. 70%
12. Estimate the prevalence of diabetes mellitus for a screened workforce of 10,000 employees among whom 1000 workers are detected with diabetes mellitus during the initial screening, and 45 new diagnoses are detected at a subsequent annual screen 1 year later.
13. Estimate the incidence rate (per person-year) of new case development in the population described in question 12, assuming no entries from or losses of patients and no deaths from other causes.
14. Estimate the 5-year cumulative risk of developing diabetes mellitus in the population described in question 12, assuming no entries from or losses of patients and no deaths from other causes.
15. A Diabetes survey was conducted in 1999 in a certain town with the population of 9,000 people in the early of year and 10,000 people at the end of this year. There are 800 people with diabetes in the early of this year and 200 diabetic patients were newly diagnosed within this year. 35 people died in diabetes in the year. 1) The cumulative incidence of diabetes in the town in 1999.
2) The mortality rate of diabetes in the town in 1999.
3) The case fatality of diabetes in the town in 1999.
4) The prevalence of diabetes in the town during 1999.
16. Cancer registries report 40 new cases of bladder cancer per 100,000 men per year. Cases were from a complete count of all patients who developed bladder cancer in several regions of the United States, and the number of men at risk was estimated from the census data in those regions. Which rate is this an example of? A. Point prevalence B. Period prevalence C. Incidence density D. Cumulative incidence E. Complication rate 17. Sixty percent of adults in the U.S. population have a serum cholesterol>200mg/dL(5.2mmol/L). Which rate is this an example? A. Point prevalence B. Complication rate C. Incidence density D. Cumulative incidence E. Period prevalence 18. The incidence of rheumatoid arthritis is about 40/100,000/year and the prevalence is about 1/100 persons. On average, how many years does the disease persist? A. 10 B. 25 C. 33 D. 40 E. 50 19. Which of the following would not increase the observed incidence of disease? A. More aggressive efforts to detect the disease B. A true increase in incidence C. A more sensitive way of detecting the disease D. A lowering of the threshold for diagnosis of disease
E. Studying a larger sample of the population 20. Last year, 800,000 Americans died of heart disease or stroke. Which of the following best describes this statistic? A. Incidence density B. Point prevalence C. Cumulative incidence D. Period prevalence E. None of the above
LAB 2 QUESTIONS Read the following and select the best response (review for the case-control study and cohort study) 1. In a case-control study of oral contraceptives and myocardial infarction (heart attact), exposure to birth control pills was abstracted from medical records at the time of the myocardial infarction. Results might be biased toward finding an association by all of the following except: A: Physicians might have asked about use of birth control pill use more carefully in cases. B: Having a myocardial infarction might have led to oral contraceptive use. C: Physicians might have been more likely to record birth control use in cases. D: Medical record abstractors might have looked for evidence of oral contraceptive use more carefully if they knew a patient had had a myocardial infarction. E: Patients might have recalled exposure more readily when they had a heart attack. 2. Investigators in Europe did a case-control study, nested in a multicounty cohort of more than 520,000 participants, of vitamin D concertation and the risk of colon cancer. They studied 1,248 cases of incident colon cancer arising in the cohort and an equal number of controls, sampled from the same cohort and matched by age, sex, and study center. Vitamin D was measured in blood samples taken years before diagnosis. Vitamin D levels were lower in patients with colon cancer, independent of a rich array of potentially confounding variables. The study results could be described by any of the following except: A. Vitamin D levels were associated with colorectal cancer. B. Vitamin D deficiency was a risk factor for colorectal cancer. C. Nesting the study in a large cohort was a strength of the study. D. The results might have been confounded with unmeasured variables related to vitamin D levels and colorectal cancer. E. Vitamin D deficiency was a cause of colorectal cancer
3. Which of the following is the most direct result of a case-control study? A. Prevalence B. Risk difference
C. Relative risk D. Incidence E. Odds ratio
4. The epidemic curve for an acute infectious disease describes: A. The usual incubation period for the causal agent B. A comparison of illness over time in exposed versus non- exposed people C. The onset of illness in cases over time D. The duration of illness, on average, in affected individuals E. The distribution of time from infection to first symptoms
5.Which of the following is the best reason for doing a case-control analysis of a cohort study? A. Case-control studies are a feasible way of controlling for confounders not found in the cohort dataset. B. Case-control studies can provide all the same information more easily. C. Case-control studies can determine incidence of disease in exposed and non-exposed, members of the cohort. D. Case-control studies are in general stronger than cohort studies.
6. The best way to identify cases is to obtain them from: A: A sample from the general (dynamic) population B: Primary care physicians’ offices C: A community D: A cohort representative of the population E: A hospital
7.What is the best reason to include multiple control group in a case-control study? A. B. C. D. E.
To obtain a stronger estimate of relative risk There are a limited number of cases and an ample number of potential controls To control for confounding To increase the generalizability of the result The main control group may be systematically different from cases(Other than on the exposure of interest)
8.Case-control studies can be used to study all of the following except: The early symptoms of stomach cancer Risk factors for sudden infant death syndrome The incidence of suicide in the adult population The protective effect of aspirin Modes of transmission of an infectious disease
A. B. C. D. E.
9.In a case-control study of exercise and sudden cardiac death, matching would be useful: To control for all potential confounding variable in the study To make cases and controls similar to each other with respect to a few major characteristics To make it possible to examine the effects of the matched variables on estimated relative risk. To test whether the right controls were chosen for the cases in the study. To increase the generalizability of the study.
A. B. C. D. E.
10. In a case-control study of whether prolonged air travel is a risk factor for venous thromboembolism, 60 out of 100 cases and 40 out of 100 controls had prolonged air travel. What was the crude odds ratio from this study? A. B. C. D. E.
0.44 1.5 2.25 3.0 Not possible to calculate
11.A population-base case-control study would be especially useful for studying: A. B. C. D. E.
The population attributable risk of disease Multiple outcomes (disease) The incidence of rare diseases The prevalence of disease Risk factors for disease
12. Case-control studies would be useful for answering all of the following questions except: A. B. C. D. E.
Do cholesterol-lowering drugs prevent coronary heart disease? Are complications more common with fiberoptic cholecystectomy than with conventional (open) surgery? Is drinking alcohol a risk factor for breast cancer? How often do complications occur after fiberoptic cholecystectomy? How effective are antibiotics for otitis media?
13. Which of the following statements is not correct for both prospective and retrospective cohort studies? A. B. C. D.
They measure incidence of disease directly. They allow assessment of possible associations between exposure and many diseases. They allow investigators to decide beforehand what data to collect. They avoid bias that might occur if measurement of exposure is made after the outcome of interest is known.
Questions 14-16 are based on the following example: A
AGE
NON-SMOKERS
SMOKERS
45-49
7.4
29.7
65-69
80.2
110.4
study was done examinging the relationship of smoking, stroke, and age. The 12-year incidence per 1,000 persons (absolute risk) of stroke according to age and smoking status was:
14. What was the relative risk of stroke of smokers compared to non-smokers in their 40s? A. 1.4 B. 4.0 C. 22.3 D. 30.2 E. 72.8 F. 80.7 15. What was the attributable risk per 1,000 people of stroke among smokers compared to non-smokers in their 60s? A. 1.4 B. 4.0 C. 22.3 D. 30.2 E. 72.8 F. 80.7 16.Which of the following statements about the study results is incorrect? A. To calculate population-attributable risk of smoking among people in their 60s, additional data are needed. B. More cases of stroke due to smoking occurred in people in their 60s than in their 40s. C. When relative risk is calculated, the results reflect information about the incidence in exposed and unexposed persons, whereas the results for attributable risk do not. D. The calculated relative risk is a stronger argument for smoking as cause of stroke for persons in their 40s than the calculated risk for persons in their 60s. E. Depending on the question asked, age could be considered either a confounding variable or an effect modifier in the study. 17. In a study to determine if regularly taking aspirin prevents cardiovascular death, aspirin users died as often as non-users. However, aspirin users were sicker and had illnesses more likely to be treated with aspirin. Which of the following methods is the best way to account for the propensity of people to take aspirin? A. Calculate the absolute risk of cardiovascular death in the two groups and the risk difference attributable to using aspirin. B. Create subgroups of aspirin users and non-users with similar indications for using the medication and compare death rates among the subgroups. C. For each person using aspirin, match a non-user on age, sex, and comorbidity and compare death rates in the two groups.
INTRODUCTION TO EBM 1. WHAT IS EBM ? > EVIDENCE BASED MEDICINE > It is the integration of best research evidence with clinical expertise and patient values.
2. WHAT ARE THE 4 STEPS OF EBM ?
I. II. III. IV.
Formulate an answerable question Track down the best evidence Critically appraise the evidence Individualize, based clinical expertise and patient concerns
3. WHAT IS A GOOD CLINICAL QUESTION ?
⁻ Good questions are the backbone of practicing EBM. ⁻ It takes practice to ask the well-formulated question. ⁻ Directly relevant to the care of the patient and our knowledge deficit. ⁻ Contains the following elements: ⁻ the patient or problem being addressed ⁻ the intervention or exposure(therapy, diagnostic) being considered ⁻ the comparison intervention or exposure, when relevant ⁻ the clinical outcomes of interest.
SYSTEMATIC REVIEWS & META-ANALYSIS 1.WHAT IS JADAD SCORE USED FOR ? WHAT CHARACTERISTICS OF STUDIES ARE EVALUATED IN JADAD ? ⁻ Jade score and T.C Chalmers score are the two examples of quality assessment instruments JADAD SCORE RANDOMIZATION (2 POINTS POSSIBLE) ⁻ ⁻ ⁻
1 point if study described as randomized Add 1 point if randomization method described and appropriate (e.g. random numbers generated) Deduct 1 point randomization described and inappropriate
DOUBLE-BLINDING (2 POINTS POSSIBLE) ⁻ ⁻ ⁻
1 point if study described as double-blinded Add 1 point if method of double-blinding described and appropriate Deduct 1 point if double-blinding described and inappropriate
WITHDRAWALS (1 POINT POSSIBLE) ⁻ Give 1 point for a description of withdrawals and drop-outs Study
Randomization
Blinding
Drop-out
1
++
+
++
2
+
++
0
3
++
0
+
4
+
++
++
5
0
++
+
2. WHAT DOES MEAN BY ‘ PUBLICATION BIAS’ ? WHAT GRAPHS SHOWS PUBLICATION ?********** ⁻ ⁻
Selective publication of articles that show positive treatment of effects and statistical significance. Hence, it is important to search for unpublished studies through a manual search of conference proceedings, correspondence with experts, and a search of clinical trials registries. -
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study showing beneficial effects of new treatment more likely to be published than one showing no effect negative trials assumed to contribute less; never show up in the literature base use several approaches to avoid this Use Funnel Plots to examine the influence of publication bias
FUNNEL PLOT is used as a way to assess publication bias in meta-analysis. It plots the effect size against the sample size of the study or the standard error of effect size (related to n). -
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Plots the effect size against the sample size of the study To study a funnel plot, look at its LOWER LEFT corner, that’s where negative or null studies are located If EMPTY, this indicates “PUBLICATION BIAS” Note that here, the plot fits in a funnel, and that the left corner is not all that empty, but we cannot rule out publication bias
3. WHAT EFFECT SIZE IS FOR CATEGORICAL MEASUREMENT ? EFFECT SIZE -
-
difference - standardized mean difference/pre-post differences ratio-odds ratio/risk ratio Coefficient-correlation/regression
COHORT STUDY DEFINITION OF THE COHORT STUDY. • A study in which a group or groups of individual (i.e., a cohort) are defined on the basis of the presence or absence of exposure to a suspected risk factor for a disease. • At the time exposure status is defined, all potential subjects must be free from the disease under investigation • Eligible participants are then followed over a period of time to assess the occurrence of that outcome.
PROSPECTIVE AND RETROSPECTIVE COHORT STUDIES - A cohort study is usually prospective, that is, exposure to the risk factor and subsequent health outcomes are observed after the beginning of the study. - Occasionally, a cohort study is retrospective (or historical), that is, it utilizes information on prior exposure to the risk factor and subsequent disease status.
PROSPECTIVE COHORT STUDY Strengths: 1. Time sequence strengthens inference about cause 2. More accurate measurement of prognostic or risk factors (do not need to reconstruct past exposures) 3. More complete measurement of confounding 4. Can study situations where randomization is not possible Weaknesses: 1. Expensive and time consuming (inception and follow-up) 2. Large numbers required to study rare outcomes 3. Difficult to study chronic diseases with long latency
RETROSPECTIVE COHORT STUDIES Strengths: 1. Cohort easier to assemble (inception period in past). 2. Baseline measurements already available. 3. Follow-up period already taken place. 4. Less costly and time-consuming. Weaknesses: 1. No control over the quality of past measurements. 2. Incomplete data sets. 3. Control for confounding may be incomplete.
ATTRIBUTE
RETROSPECTIVE APPROACH
PROSPECTIVE APPROACH
Information
Less complete & accurate
More complete & accurate
Discontinued exposures
Useful
Not useful
Emerging new exposures
Not useful
Useful
Expense
Less costly
More costly
Completion time
Shorter
Longer
MEASURE OF EFFECT :: RISK RATIO, RISK DIFFERENCE, ATTRIBUTABLE RISK PERCENTAGE, RATE RATIO RISK RATIO • Among exposed persons, the risk (R) defined as Exposed persons who die All exposed persons A AC
R (exposed)
• Among unexposed persons, the risk of death is defined as Unexposed persons who die All unexposed persons B BD
R (unexposed)
• One approach to contrasting the risk in two groups is to create a ratio measure. The risk ratio (RR) or relative risk is RR
R(exposed) A AC R(unexposed) B B D
RR=1 The exposed and unexposed persons have the same risk of death and exposure is not related to the outcome. (ie, the null value)
RR>1 The risk among exposed persons is greater than the corresponding risk among unexposed persons, (ie, hazardous exposure)
RR<1 The risk among exposed persons is smaller than the corresponding risk among unexposed persons (ie, beneficial exposure)
RISK DIFFERENCE
ATTRIBUTE RISK PERCENTAGE • in which the risk difference is expressed as a percentage of the total risk experienced by the exposed group:
R (exposed) R (unexposed) 100 R (exposed) A AC B B D 100 A AC
ARP
RATE RATIO •
•
•
In a cohort study, the measured outcome may be an incidence (or mortality) rate rather than a risk. Summary format of rate data from a cohort study: Exposed Persons
Unexposed Persons
Total
Number of outcomes
A
B
A+B
Person-time (PT)
PT (exposed)
PT (unexposed)
PT (total)
Rate Ratio is derived from :: Rate of outcome among exposed persons Rate of outcome among unexposed persons A PT (exposed) B PT (unexposed)
Rate ratio=
•
The magnitude of the rate ratio is interpreted in the same manner as the risk ratio: RR< 1 : protective effect, RR =1: no effect, RR> 1: harmful or risk effect of exposure
EXERCISE I. Glossary 1. RISK FACTOR The term “ risk factor “ is commonly used to describe factors that are positively associated with the risk of development of a disease but that are not sufficient to cause the disease. 2. DOUBLE BLIND (newly added{instead previously it was SINGLE BLIND}) It’s the masking of treatment as Neither patient nor health care provider know treatment. [SINGLE BLIND :: Patient does not know treatment]
3.OPEN TRIAL (newly added{instead previously it was RANDOMIZED CLNICAL TRAIL-RCT}) It is a type of clinical trail in which both the researchers and the participants know which treatment is being administrated. 4.CLINICAL TRIAL A prospective study comparing the effect and value of interventions against a control in human beings.
5. CAUSALITY Change in one variable [cause] is followed by change in the other variable [effect]
6.SCREENING (newly added{instead previously it was CLINICAL EPIDEMOLOGY}) The PRESUMPTIVE identification of UNRECOGNIZED disease or defect by the application of tests, exams or other procedures which can be applied RAPIDLY to sort out apparently well persons who PROBABLY have a disease from those who PROBABLY do not. 7. PROGNOSIS Prognosis is a probabilistic prediction of the future course of disease following its onset(ആക്രമം).
8.TEMPORALITY > The causal factor must precede the disease in time. This is the only one of Hillis criteria that everyone agrees with. > Prospective studies do a good job establishing the correct temporal relationship between exposure and a disease.
9.PLACEBO EFFECT A placebo , an intervention that is indistinguishable from the active treatment – in physical appearance, colour, taste and smell but does not have a specific, known mechanism of action.
II. Choice 1. Which are not purposes of epidemiology? A. Identify causes and risk factors for disease. B. Determine the extent of disease in the community. C. Evaluate preventive and therapeutic measures D. Study natural history and prognosis of disease. E. Explore biases, uncertainties and methodological weaknesses. 2. Which is not use of epidemiology? A. disease surveillance
B. causation
C. natural history of disease
D. description of health status in population
E. diagnosis and treatment of a patient
3. Which is correct about Factors in causation? A. Predisposing factors, such as low income, poor nutrition, bad housing B.Enabling (or disabling) factors such as age, sex, or specific genetic traits C. Precipitating factors such as low income, poor nutrition, bad housing D. Reinforcing factors such as repeated exposure E. All answers above are not correct.
4. Randomized, controlled, blinded trials are the standard of excellence for comparisons of treatment effects over time. However, its limitation is: A. adequate patient
B. relatively inexpensive
D. conclusive evidence
E. more generalizable
C. relatively short time
5. Which is not correct description of temporal relationship in causal inference? A. Prospective studies do a good job establishing the correct temporal relationship between an exposure and a disease. B. The larger the association, the more likely the exposure is causing the disease. C. Strong associations are more likely to be causal because they are unlikely to be due entirely to bias and confounding. D. Weak associations may be causal but it is harder to rule out bias and confounding. E. The temporal relationship is usually self-evident when measurements of the possible cause and effect are made at the same time.
6. Associations are not measured by A. relative risk
B. odds ratio
C. absolute risk
D. statistical tests
E. prevalence
7. which is wrong description about causality? A. Association is not equal to causality B. Causality is that change in one variable is followed by change in the other variable C.Counterfactual thinking is fundamental in causality D.Need to exclude chance and bias as explanations before moving to consider likelihood of cause and effect. E. The causal factor may precede the disease in time
8. Which is not correct about the strength of the association? A. The larger the association, the more likely the exposure is causing the disease. B. Example: Relative risk of lung cancer in smokers vs. non-smokers =9; Relative risk of lung cancer in heavy vs. non-smokers = 20. C. Strong associations are more likely to be causal because they are unlikely to be due entirely to bias and confounding. D. Weak associations are more likely to be causal.
9. Patients in clinical trials are usually a highly selected, biased sample of all patients with the condition of interest, no because of A. entry criteria
B. exclusion criteria
D. stable population
E. Ineligible
C. Eligible but not enrolled
10. Which is the definition of Placebo effect? A. an intervention that is indistinguishable from the active treatment—in physical appearance, color, taste, and smell—but does not have a specific, known mechanism of action. B. an intervention that is distinguishable from the active treatment—in physical appearance, color, taste, and smell—but does not have a specific, known mechanism of action. C. People tend to change their behavior because they are the target and attention in a study, regardless of the specific nature of the intervention they might be receiving. D. People tend to change their behavior because they care about the specific nature of the intervention they might be receiving. E. Placebos are used only when no standard treatment exists
11. Which is wrong description about blinding? A. Blinding is ware of which patients are intervention group, or control group
B. Blinding is masking of treatment from patient, clinician, designer, and analyst C. Blinding is the protection against bias in outcome assessment D. Blinding sometimes may not be feasible E. Blinding is of greatest importance if outcome is subjective
12. Which is the aim of Phase II in a clinical trial? A. In vitro studies and animal models B. Maximum Tolerated Dose (MTD) C. Evaluation of biologic activity and adverse events D. Comprehensive analysis of efficacy and safety E. Postmarketing surveillance
13. One of your patients read that cell phones cause brain cancer, and she wants to know your opinion. You discover that the incidence of malignant brain tumors is increasing in the United States. Results of several observational studies of cell phone use and brain cancer have not agreed with each other. A randomized controlled trial might resolve the question. What is the main reason why a randomized controlled trial would be unlikely for this question? A. it would cost too much
B. people would not agree to be randomized to cell phone use.
C. it would take too long
D. even if done well, a randomized trial could not answer the question.
14. Which of the following is the most accurate description of a causal relationship? A. Tuberculosis has a single cause, the tubercle bacillus. B. Most genetic diseases are caused only by an abnormal gene. C. Coronary heart disease has multiple interacting causes. D. Effective treatment has been the main cause of decline in tuberculosis rates.
15. Which of the following is not one of the Bradford Hill criteria for causation? A. Dose-response
B. Statistical significance
C. Reversibility
D. Biologic plausibility
E. Analogy
16. Randomized controlled trials are the strongest research designs for establishing cause and effect. Which of the following is the main limitation of trials for this purpose? A. Randomized trials cannot control for unmeasured confounders. B. Clinical trials may not be ethical or feasible for some questions. C. Type of study design is only a crude measure of the scientific strength D. Results of poorly designed and conducted trials are no better than for observational studies
17. Which of the following provides the strongest evidence for a cause-and-effect relationship? A. Observational studies that have controlled for bias and minimized the role of chance. B. A biologic mechanism can explain the relationship. C. The purported cause clearly precedes the effect. D. There is a dose-response relationship. E. The evidence as a whole is consistent with the Bradford Hill criteria.
18. Which of the following is usually learned from a Phase III drug trial? A. The relationship between dose and efficacy
B. Rates of uncommon side effects
C. Efficacy or effectiveness
D. The dose range that is well tolerated
19. Which of the following is the main advantage of randomized controlled trials over observational studies of treatment effects? A. Fewer ethical challenges
B. Prevention of confounding
D. Quicker answer
E. Less expensive
C. Resemble usual care
20. In a randomized controlled trial of two drugs for coronary artery disease, the primary outcome is a composite of acute myocardial infarction, severe angina pectoris, and cardiac death. Which of the following is the main advantage of this approach? A. There are more outcomes events than there would be for any of the individual outcomes. B. All outcomes are equally affected by the interventions. C. The trial has more generalizability. D. Each of the individual outcomes is important in its own right. E. If one outcome is infrequent, others make up for it.
Questions 21-25 are based on the following example. For each question, select the best answer. A study was made of symptoms and physical findings in 247 patients evaluated for sinusitis. The final diagnosis was made according to x-ray findings (gold standard). Ninety-five patients had sinusitis, and 49 of them also had facial pain. One hundred fifty-two did not have sinusitis, and 79 of these patients had facial pain. 21. What is the sensitivity of facial pain for sinusitis in this study? A. 38%
B. 48%
C. 52%
D. 61%
C. 52%
D. 61%
22. What is the specificity? A. 38%
B. 48%
23. If the doctor thought the patient had sinusitis because the patient had facial pain, for what percent of patients would she be correct? A. 38%
B. 48%
C. 52%
D. 61%
24. If the doctor thought the patient did not have sinusitis because the patient did not have facial pain, for what percent of patients would she be correct? A. 38%
B. 48%
C. 52%
D. 61%
25. How common was sinusitis in this study? A. 38%
B. 48%
C. 52%
D. 61%
III Long questions 1. WHY DO PHYSICIAN LEARN CLINICAL EPIDEMIOLOGY? PLEASE YOU GIVE SOME SUGGESTIONS FOR THIS COURSE. ⁻ To collect data on usual and unusual events, conditions & population groups ⁻ To test hypotheses formulated from observation and/or intuition ⁻ Ultimately, to understand better one’s world and make “sense of it” ⁻ We can describe healthy phenomenon to ------ and compare health conditions in different countries. ⁻ Certainly, we pay more attention to explore what cause disease. 2. HOW TO DISTINGUISH BETWEEN ASSOCIATION AND CAUSE IN CLINICAL RESEARCH. ASSOCIATION: Studies seek links or associations: Rarely cause and effect (RCT) ⁻ Associations measured by RELATIVE RISK, ODD RATIO, ABSOLUTE RISK, OR STATISTICAL TESTS. ⁻ Explanations for associations include: CHANCE (coincidence) – BIAS, including confounding ⁻ The association is observed repeatedly in different persons, places, times and circumstances. IN CAUSE: We need to exclude chance and bias as explanations before moving to consider likelihood of cause and effect. Its characteristics are :: - Must precede the effect (proximate vs distant) - Can be either host or environmental factors (eg., characteristics, conditions, actions of individuals, events, natural, social or economic phenomena) - POSITIVE presence of causative exposure; NEGATIVE lack of preventive exposure. - CAUSALITY: Change in one variable(cause) is followed by change in other variable(effect). 3. WHAT IS CAUSAL INFERENCE? LIST THE CONSIDERATIONS COMMONLY USED TO ASSESS THE CAUSAL NATURE OF OBSERVED ASSOCIATIONS. The process by which we make a casual inference – JUDGEMENTS LINKING POSTULATED CAUSES & THEIR OUTCOMES in a major theme of general philosophy of science and the concept of cause has different meanings in different contexts. CONSIDERATIONS USED TO ASSESS THE CAUSAL NATURE :: 1. TEMPORAL RELATION :: Does the cause precede the effect ? (essential) 2. PLAUSIBILITY :: Is the association consistent with other knowledge ? (mechanism of action, evidence from exp. animals) 3. CONSISTENCY :: Have similar results been shown in the other studies. 4. STRENGTH :: What is the strength of association between the cause and the effect ? (Relative Risk) 5. DOSE-RESPONSE RELATIONSHIP :: Is increased exposure to the possible cause associated with increased effect ? 6. REVERSIBILITY :: Does the removal of possible cause lead to reduction of disease risk ? 7. STUDY DESIGN :: Is evidence based on strong study design. 8. JUDGING EVIDENCE How many lines of evidence lead to conclusion?
4. WHAT IS A CLINICAL TRIAL? BASIC STEPS IN CONDUCTING A RANDOMIZED CLINICAL TRIAL. The prospective study comparing the effect and value of interventions against a control in human beings. BASIC STEPS IN CONDUCTING A RCT :: 1. Drawing up a protocol 2. Selecting reference and experimental populations 3. Randomization 4. Manipulation or intervention 5. Follow up 6. Assessment of outcome
5. PLEASE GIVE THE CRITERIA FOR EVALUATING A SCREENING TEST. • Validity: provide a good indication of who does and does not have disease (get the correct result) -Sensitivity of the test -Specificity of the test • Reliability: (precision): gives consistent results when given to same person under the same conditions (get same result each time) • Yield: Amount of disease detected in the population, relative to the effort -Prevalence of disease/predictive value