Page:of 8 Automatic Zoom Page 1 Sample exam questions for Introduction to Epidemiology and Public Health Note: Questions can be multiple choice (indicate the one correct answer) or multiple response (squares indicate all answers that are correct). 1. To be causally associated with disease, the etiological factor should fulfill the following criteria: Indicate all that apply. The factor is present in all subjects with the disease. Elimination of the factor reduces risk of the disease. The exposure to this factor should p recede the development of the disease. The factor is more prevalent among those with the disease than among those without the disease. 2. At the start of a cohort study the exposure is determined with the help of a questionnaire. During the study the re is no "loss to follow up". At the end of the follow up time the number of cases is known and is divided into exposed and unexposed. The odds ratio (OR) is used as the association measure. Which comment is the most appropriate here? a. Researchers should ha ve better calculated the risk ratio (=incidence proportion ratio). b. The OR has no useful interpretation. c. Researchers should have better calculated the incidence rate ratio. d. The OR approaches the incidence rate ratio. 3. During a study of 20 years five people are followed to measure the occurrence of upper respiratory tract infection. As this infection can occur more than once, all disease events are included in this study. 1 person is lost to follow up after 1.5 years. 2 persons died respectively after 10 and 15 years from a different cause. 1 person got the first respiratory tract infection after seven years and the second infection after 12 years of follow up. Both infections take half a year of recovery. This person is followed up until the end of the study. One person is followed up the whole period without occurrence of disease. What is de incidence rate in this study ? a. 0.06 per person year b. 0.03 per person year c. 0.15 per person year d. 0.08 per person year Page 2 4. What is the fraction of cases with the disease among the exposed that is attributable to the exposure? Unexposed Exposed Disease 9 17 No disease 7 5 a. 0.27 b. 0.60 c. 0.30 d. 0.77 5. The incidence rate (IR) differs from the incidence proportion (IP) because... e. IP can be assessed in a closed population, IR not. f. IR can be assessed in an open population, IP not. g. IP takes competing mortality into account; IR does not. h. IR can be assessed more precisely than IP 6. If you want to know the proportion of the disease that could be prevented by eliminating the exposur e in the entire study population, you should calculate the a. attributable fraction b. attributable risk c. population attributable risk percentage d. negative predictive value 7. Precise measurement of exposure is important in epidemiologic research. Namely, when the exposure is not precisely measured the association between exposure and effect is likely to be... a. overestimated b. confounded c. underestimated d. random 8. Which of the following designs is/are suitable for studying a genetic polymorphism in relation to risk of diabetes mellitus? Indicate all that apply. Case control study Cross sectional study Cohort study Randomized, controlled trial Page 3 9. The Cancer and Steroid Hormone (CASH) study, in which women with breast cancer and a comparable group of women without breast cancer were asked about their prior use of oral contraceptives is an example of which type(s) of study? Indicate all that apply. clinical trial cohort study cross sectional survey case control study observational study experimental study 10. The precision of an estimate of a relative risk depends on the ... a. generalisability b. size of the stud y c. validity of the s tud y d. presence of bias 11. In a cohort study the relative risk for COPD for moderate smokers versus non smokers was 4. For heavy smokers compared to non smokers the relative risk was 10. What would have been the relative risk for COPD in this study if the hea vy smokers were used as the reference category? a. for non smoking 0.1 and for moderate smoking 0.4 b. for non smoking 0.2 and for moderate smoking 0.6 c. for non smoking 4 and for heavy smoking 10 d. this cannot be calculated with the available data 12. An epidemiologi st in Tanzania wants to study the efficacy of iron supplementation for the prevention of HIV infection. He wants to make sure that only subjects who are (still) free of HIV infection are enrolled in his trial. Therefore, he screens a large group of people using a diagnostic test. Based on the outcome of the test, he decides who could participate in his iron supplementation trial. For this purpose, it is very important that the diagnostic test has a high... a. sensitivity b. positive predictive value c. specificity d. negative predictive value 13. A diabetes test is being applied in a population of 5000 men. Previous evaluation of the diabetes test in a different population showed a sensitivity of 70% and an specificity of 80%. The prevalence of diabetes is 0.5%. What is the diagnostic value of a positive test in this situation? a. 2% b. 47 % c. 4% d. 7 0% Page 4 14. Information bias in a cohort study can be avoided by ensuring that... Indicate all that apply. no competing diseases do occur. follow up is complete. the persons who assess the disease are not aware of the exposure of the participant. disease assessment is highly standardized. the persons who collect the data are not aware of the study hypothesis. 15. A cohort study shows a RR of 1.8 (95% CI 1.4 2.2) for alco hol consumption and breast cancer. Another cohort study shows a RR of 1.8 (95% CI 0.6 3.5) for smoking and breast cancer. What can be concluded from the results of this study? Indicate all that apply. Both associations are likely to be due to chance. Both associations are biased. The study on smoking is probably smaller than the study on alcohol. Alcohol and smoking both cause breast cancer. 16. When studying diet and risk of chronic diseases, a cohort study generally has the following advan tage compared to a case control study: a. Potential confounders can be taken into account b. Selection bias does not occur c. Various dietary exposures can be studied at the same time d. It has higher internal validity 17. What is a disadvantage of a cohort study compared to a clinical trial? a. The external validity is lower b. It is more prone to confounding c. It is less suitable for studying clinical outcomes d. Participants can drop out during follow up 18. The Framingham Study, in which a group of residents have been follo wed since the 1950s to identify occurrence and risk factors for heart disease, is an example of which type(s) of study? cohort case control experimental observational clinical trial cross sectional Page 5 19. Researchers prospectively follow a group of 100 vegetarians and 200 non vegetarians. After 30 years of follow up, 8 of the vegetarians and 20 of the non vegetarians develop heart disease. The 95% confidence interval on the relative risk of 0.8 ranges from 0.6 to 0.9. Select the be st statement. a. Vegetarians were 80% less likely to develop heart disease during 30 years of follow up compared with non vegetarians. b. The researchers should have calculated an odds ratio rather than a relative risk. c. The relative risk of 0.8 is not statisti cally significant as the 95% confidence interval contains the value 0.8. d. Vegetarians were 20% less likely to develop heart disease during 30 years of follow up compared with non vegetarians. 20. In the Netherlands there is an increase in the prevalence of cardiovascular diseases. This is a consequence of a. deterioration of the food pattern b. increase in hypertension c. improved treatment d. increase in obesity 21. General practitioners decide to intensify pharmacological treatment of patients when their absolute 10 year risk of cardiovascular mortality exceeds 20%. Which risk factors form the basis for calculating this absolute risk? a. Age, gender, smoking, isolated systolic hypertension an d serum triglyceride levels b. Age, gender, smoking, blood pressure an d presence of diabetes mellitus c. Age, gender, smoking, systolic blood pressure an d serum total cholesterol d. Age, gender, smoking, body mass index and family history 22. In a hospital based study of the association between coffee consumption and the occurrence of stroke, a group of patients hospitalized after suffering a stroke was compared to a control population hospitalized for other reasons. The patients hospitalized for stroke were found to consume significantly more coffee than the controls. All of the following sta tements represent possible explanations for the observed positive association between coffee consumption and stroke, EXCEPT : a. Heavy coffee consumers may also be heavy smokers, so smoking rather than coffee drinking is the relevant causal factor b. The patien ts restricted their coffee intake after suffering a stroke. c. The hospitalized controls consume less coffee, on the average, than individuals in the general population, resulting in a spurious association between coffee consumption and stroke. d. Excessive co ffee consumption can cause a stroke. 23. Select the correct statement concerning the selection of controls in a case control study: a. Randomization can help assure comparability of cases and controls. b. Matching can be used to reduce confounding bias. c. It is best to identify controls with conditions that are related to the outcome in the case control study. d. It is less important to assure comparability of cases and controls in a case control study than comparability of study arms in a randomized controll ed trial. Page 6 24. In a case control study the association was examined between smoking and risk of Parkinson's disease. The table below provides the results. Which of the following odds ratios is correct? Controls Cases Smokers 55 30 Non smokers 45 70 a. 0.35 b. 2.85 c. 1.83 d. 0.55 25. Indicate three types of cancers that are most frequently occurring in Westernized countries. lymphoma bladder cancer cervical cancer colon cancer prostate cancer breast cancer 26. An epidemiologist performed a double blind, randomized, placebo controlled trial to examine the effect of fish oil supplementation on memory complaints. In the group that received fish oil, 19% of the participants forgot to take their daily supplements during the study whereas this was only 3% in the placebo group. Is this a problem? a. Yes, because this affects the external validity of the study. b. Yes, because the study outcome can be biased. c. No, because participants and investigators were blinded towards the type of treatment in both g roups d. No, because all confounders were equally distributed over both groups due to randomization 27. An epidemiologist wants to assess the effect of tea drinking on blood pressure. He decides to do an intervention study. Which of the following measures does not increase the internal validity of the study? a. Careful monitoring of blood pressure during the study b. Inclusion of a control group c. Randomization d. Random selection of participants from the general population 28. The main advantage of a randomized controlled trial (RTC) compared to all other epidemiology study designs is that the RCT: a. equally distributes characteristics that may be independent risk factors for the outcome of interest over the study arms. b. is prospective thereby eliminating the need for histor ical data. c. is less expensive. d. guarantees that confounding bias will not occur. Page 7 29. A pharmaceutical company showed the following in an article: "1500 subjects with a cold were treated with our new medicine. Within three days, 95% were asymptomatic and this result was statistically significant." The company claims the new medicine was effective. Is this conclusion justified? a. Yes, because the effect was very large (95% of the subjects benefitted from treatment). b. No, because statistical significance indic ates that the null hypothesis ("no effect") was correct. c. No, because no control group was involved in the study. d. Yes, because the effect of treatment could not be explained by chance. 30. Public health surveillance includes various activities. Which one is not part of public health surveillance? a. Data collection b. Data dissemination c. Disease control d. Data analysis 31. The problem of confounding can be solved by... a. ch o osing a prospective design. b. increasing the precision of the measurements. c. stratification during data analysis. d. this cannot be solved. 32. The number of DALYs (Disability Adjusted Life Years) lost in each person's life history can be calculated. By combining all life histories in this population of three persons, the population health in terms of DALYs can be described for this population. Which of the following combinations is correct? a. In the life history of person A 35 DALYs are lost and the total loss of DALYs for the population of three is 70 b. In the life history of person A 15 DALYs are lost a nd the total loss of DALYs for the population of three is 55.5 c. In the life history of person B 5 DALYs are lost and the total loss of DALYs for the population of three is 9.5 d. In the life history of person C 19.5 DALYs are lost and the total loss of DALYs f or the population of three is 79.5 33. In a study on the prevalence of disease X in nursing homes A and B you get the following data. Nursing home A = index 1 Age Persons Number of cases with disease X Prevalence rate (per 100) Young 200 4 2.0 Old 400 24 6.0 Total 600 28 4.7 Page 8 Nursing home B = index 2 Age Persons Number of cases with disease X Prevalence rate (per 100) Young 800 24 3.0 Old 100 8 8.0 Total 900 32 3.6 Nursing home A + B = standard Age Persons Number of cases with disease X Prevalence rate (per 100) Young Old Total One can calculate the standardi z ed prevalence rate and comparative mortality figure (CMF) by means of direct standardization, using the joint population of nursing home A and B as the standard. Which calculation is correct? a. The standardized rate of nursing home A is 3.3/100 b. The CMF of nursing home A is 0.97 c. The standardized rate of nursing home A is 2.4/100 d. The standardized rate of nursing home B is 6.3/10