Exercise 2 Chapters 4 & 5(2)

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Apr 3, 2024

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Exercise 2 Chapters 4 & 5 (30 questions, 1 point per question; in some rare cases, there may be more than 1 correct answer) 1. What is the case-fatality rate from influenza during the 2016 season in the young age group at Minas Tirith? Use the following table to answer the question. Number of Residents, Diagnosed Cases, and Deaths From Influenza by Age Age group No. of residents during 2016 season No. of diagnosed cases from influenza during 2016 season No. of deaths from influenza during 2016 season Young 20,000 3,000 300 Old 10,000 1,000 500 a. 15% b. 5% c. 1.5% d. 10% e. 50% 2. What is the mortality from influenza during the 2016 season in the old age group at Minas Tirith? Use the following table to answer the question. Number of Residents, Diagnosed Cases, and Deaths From Influenza by Age Age group No. of residents during 2016 season No. of diagnosed cases from influenza during 2016 season No. of deaths from influenza during 2016 season Young 20,000 3,000 300 Old 10,000 1,000 500 a. 300 deaths b. 500 deaths c. 150 deaths/1,000 people d. 100 deaths/1,000 people e. 50 deaths/1,000 people -  MORTALITY RATE 3. For a disease such as seasonal influenza, which is less fatal and of short duration? a. Incidence rates and mortality rates will be similar. b. Mortality rates will be much higher than incidence rates. c. Incidence rates will be much higher than mortality rates. d. Incidence rates will be unrelated to mortality rates. e. None of the above. 4. What is the crude death rate from disease X for City A? Use the following table to answer the question. Number of Residents and Deaths From Disease X by Age Group in City A and City B City A City B Age group No. of residents No. of deaths from disease X No. of residents No. of deaths from disease X Age < 65 3,000 30 6,000 60 Age > 65 6,000 450 3,000 225 1

a. 53 deaths/1,000 people b. 32 deaths/1,000 people c. 10 deaths/1,000 people d. 75 deaths/1,000 people e. 43 deaths/1,000 people 5. What is the age-specific mortality rate from disease X in City B for age younger than 65? Use the following table to answer the question. Number of Residents and Deaths From Disease X by Age Group in City A and City B City A City B Age group No. of residents No. of deaths from disease X No. of residents No. of deaths from disease X Age < 65 3,000 30 6,000 60 Age > 65 6,000 450 3,000 225 a. 53 deaths/1,000 people b. 32 deaths/1,000 people c. 10 deaths/1,000 people d. 75 deaths/1,000 people e. 43 deaths/1,000 people 6. Calculate the age-adjusted death rate from disease X in cities A and B by the direct method, using the total of both cities as the standard population. What is the age-adjusted death rate from disease X for City B? Use the following table to answer the question. Number of Residents and Deaths From Disease X by Age Group in City A and City B City A City B Age group No. of residents No. of deaths from disease X No. of residents No. of deaths from disease X Age < 65 3,000 30 6,000 60 Age > 65 6,000 450 3,000 225 a. 53 deaths/1,000 people b. 32 deaths/1,000 people c. 10 deaths/1,000 people d. 75 deaths/1,000 people e. 43 deaths/1,000 people 7. Which of the following statements is the most accurate interpretation of disease occurrence in City A and City B? Use the following table to answer the question. Number of Residents and Deaths From Disease X by Age Group in City A and City B City A City B Age group No. of residents No. of deaths from disease X No. of residents No. of deaths from disease X Age < 65 3,000 30 6,000 60 Age > 65 6,000 450 3,000 225 2

a. The age-adjusted mortality rate of City A is still higher than the mortality rate of City B, as compared with the crude mortality rate. b. The age-adjusted mortality rates for City A should be used to make decisions regarding allocation of funding for hospital care of the dying in City A. c. For direct age-adjustment, the weight for a given age category is the percentage of deaths for that age grou d. For direct age-adjustment, the weight for a given age category is the number of individuals in the standard population for that age group. e. The difference in the adjusted mortality rates between City A and City B is always attributable to differences in age composition between the two populations. 8. In 2016 there were 7,467 million people in the world. According to the World Health Organization, in the same year there were 56.9 million deaths worldwide; of those, 15.2 million were due to ischemic heart disease or stroke. What was the proportionate mortality of those two causes combined for that year? a. 0.8% b. 0.2% c. 3.7% d. 13.5% e. 26.7 % 9. According to the Centers of Disease Control and Prevention (CDC), during the Ebola outbreak of 2014 in West Africa, there were a total of 14,124 Ebola cases in Sierra Leone and 3,956 deaths due to Ebola. What was the case fatality rate in that country? a. 3.5% b. 22% c. 28% d. 3,956 e. 14,124 10. A researcher finds that the standardized mortality rate (SMR) for epidemiologists compared with the general population is 100. What does that mean? a. The observed number of deaths for epidemiologists is the same as the expected. b. Epidemiologists have a mortality rate 100 times greater than the general population. c. Epidemiologists have a mortality rate 100 times lower than the general population. d. The general population experience a mortality rate increased as compared with epidemiologists. e. Nothing can be said with this information. 11. The mayor of Baby City is interested in comparing the infant mortality rate (infants are defined as babies younger than the age of 12 months) of Baby City with the infant mortality rate of Adult City. He argues that the age distributions of these cities are very different and therefore asks you to calculate the age-adjusted infant mortality rate. What is the best approach? a. Use direct adjustment. b. Use indirect adjustment. c. Calculate the standardized mortality ratio. d. Explain that no age adjustment is needed when comparing with age-specific mortality rates. e. Use the World Health Organization standard population to calculate an adjusted rate. 12. City A suffered some political changes and was divided into two cities named Alpha and Beta. Five years after the division, mortality rates in both cities are compared. The all-cause mortality rate in City Alpha is much higher than the rate in Beta. When looking at the demographic characteristics in the cities, you notice that the age distribution is almost exactly the same in both cities. What do you expect to find when the age-adjusted mortality rates are calculated and compared? a. City Alpha will have a much higher age-adjusted mortality rate than Beta. b. City Beta will have a much higher age -adjusted mortality rate than Alpha. c. The age-adjusted mortality rate will be much lower than the unadjusted rate in Alpha. d. The age-adjusted mortality rate will be much lower than the unadjusted rate in Beta. 3

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e. The answer cannot be determined without the actual numbers. 13. Which of the following statements about specificity is the most accurate? a. The probability that a diseased person (case) in the population tested will be identified as diseased by the test. b. The probability that a person without the disease (noncase) in the population tested will be identified as nondiseased by the test. c. The probability that a person identified as diseased by the test will be a diseased person (case) in the population. d. The probability that a person identified as nondiseased by the test will be a person without the disease (noncase) in the population. e. The probability that a diseased person (case) in the population tested will be identified as nondiseased by the test. 14. A physical examination, digital rectal exam, was used to screen for prostate cancer in 290 men with biopsy-proven prostate cancer and in 516 age- and race-matched control men, all of whom showed no evidence of cancer at biopsy. The results of the physical examination were positive in 136 cases and in 165 control men. What is the sensitivity of the physical examination? a. 32% b . 47% c. 56% d. 57% e. Cannot calculate it based on given information 15. A physical examination, digital rectal exam, was used to screen for prostate cancer in 290 men with biopsy-proven prostate cancer and in 516 age- and race-matched control men, all of whom showed no evidence of cancer at biopsy. The results of the physical examination were positive in 136 cases and in 165 control men. What is the specificity of the physical examination? a. 32% b. 47% c. 53% d. 68% e. Cannot calculate it based on given information 16. A physical examination, digital rectal exam, was used to screen for prostate cancer in 290 men with biopsy-proven prostate cancer and in 516 age- and race-matched control men, all of whom showed no evidence of cancer at biopsy. The results of the physical examination were positive in 136 cases and in 165 control men. Now, the health commissioner in City A decides to use a physical exam, digital rectal exam, as a primary screening test for prostate cancer. What will be the positive predictive value of the physical examination? a. 45% b. 47% c. 68% d. 82% e. Cannot calculate it based on given information 17. Which of the following statement about positive predictive value is the most accurate? a. Positive predictive value is a fixed characteristic of the test. It will not change over the person, place, and time. b. Positive predictive value is affected by the sensitivity of the test only. c. Specificity will not affect the positive predictive value. d. Positive predictive value is the probability that a diseased person (case) in the population tested will be identified as diseased by the test. e . None of above. 4

18. Two physicians were asked to independently classify 250 ultrasounds as positive or negative. The comparison of their classification is shown in the following table. What is the simple percent agreement between the two physicians out of the total? Use the following table to answer the question. Number of Positive and Negative Cases by Physician 1 and Physician 2 Physician 2 Physician 1 Positive Negative Positive 45 15 Negative 25 165 a. 24% b. 28% c. 53% d. 67% e. 84% 19. Two infectious disease epidemiologists want to investigate a new laboratory test that identifies tuberculosis (TB) infections. Dr. Merritt uses the standard test, which has a sensitivity of 80% and a specificity of 90%. Dr. Foundry uses the new laboratory test, which is 90% sensitive and 99% specific. In City A, it is known that 100 of 1,000 people have TB infections. What is the negative predictive value of the standard test in City A? a. 10% b. 47% c. 53% d. 80% e. 98% 20. Two infectious disease epidemiologists want to investigate a new laboratory test that identifies TB infections. Dr. Merritt uses the standard test, which has a sensitivity of 80% and a specificity of 90%. Dr. Foundry uses the new laboratory test, which is 90% sensitive and 99% specific. Now, epidemiologists decide to run those two test as sequential tests (two-stage testing). What is the effect on net sensitivity of sequential tests? a . 72% b. 80% c. 89% d. 90% e. 98% 21. Mr. Patient tested positive for disease X. He went to see Dr. Gordis and asked him what was the probability of truly being sick given the positive results of the test. To answer that question, Dr. Gordis must know what about the test? a. Sensitivity b. Specificity c. Prevalence d. Positive predictive value e. Negative predictive value 22. A patient is weighed in the hospital by a nurse, and she is told she weighs 170 pounds. The next morning she weighs herself at home, and her weight is 168 pounds. Assuming that both scales were calibrated and the patient was measured under the same circumstances (no shoes, light clothing). What can explain the difference in weight? a. Intrasubject variability b. Intersubject variability c. Intraobserver variability 5

d. Low specificity of the test e. Low sensitivity of the test 23. A 60-year-old patient was tested for Raven disease; his test came back negative. However, he feels the test might be wrong and wants to know what is the probability of not having Raven disease given that his test came back negative. Test Disease (+) No disease (  ) Total Positive (+) 84 44 128 Negative (  ) 36 836 872 Total 120 880 1,000 Using this table, answer to the following question: what proportion of the patients who tested negative are truly disease free? a. 4% b. 33% c. 66% d. 70% e. 96% 24. A 60-year-old patient, who is an epidemiologist, was tested for Raven disease; his test came back positive. However, he is curious about the sensitivity of the test. Test Disease (+) No disease (  ) Total Positive (+) 84 44 128 Negative (  ) 36 836 872 Total 120 880 1,000 Using this table, calculate the sensitivity of the test. a. 4% b. 33% c. 66% d. 70% e. 96% 25. A diagnostic test with a very high sensitivity but very low specificity has the following problem: a. It will miss a big proportion of true cases (label them as negatives). b. It will correctly identify all negative cases. c. It will label a big proportion of healthy people as sick (false-positives). d. It will be very expensive to administer. e. Specificity is the single most important characteristic of a test. 26. The following are problems generated when a patient is given a false-positive diagnosis, except : a. Generate unnecessary expenses, as those labeled positive often go through other diagnostic procedures. b. Generates anxiety and worry. c. Increased burden to the healthcare system d. The opportunity for an effective intervention is missed. e. Unnecessary treatments are administered. 27. In a community-based hypertension testing program called HT-Aware, the detection level for high blood pressure is set at 140 mmHg for systolic blood pressure. A separate testing program called HT- Warning in the same community sets the level at 130 mmHg for high systolic blood pressure. Which statements are likely to be true? a. The sensitivity of HT-Warning is greater than that of HT-Aware b. The specificity of HT-Warning is greater than that of HT-Aware c. The number of false positives is greater with HT-Warning than with HT-Aware 6

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d. The number of false negatives is greater with HT-Warning than with HT-Aware e. The sensitivity and specificity are the same for both tests 28. A school nurse examined a population of 1,000 children in an attempt to detect nearsightedness. The prevalence of myopia in this population is known to be 15%. The sensitivity of the examination is 60% and its specificity is 80%. All children labeled as "positive" (i.e., suspected of having myopia) by the school nurse are sent for examination by an optometrist. The sensitivity of the optometrist's examination is 98% and its specificity is 90%. How many children are labeled "positive" by the school nurse? a. 260 b. 250 c. 280 d. 220 e. 300 29. A school nurse examined a population of 1,000 children in an attempt to detect nearsightedness. The prevalence of myopia in this population is known to be 15%. The sensitivity of the examination is 60% and its specificity is 80%. All children labeled as "positive" (i.e., suspected of having myopia) by the school nurse are sent for examination by an optometrist. The sensitivity of the optometrist's examination is 98% and its specificity is 90%. What is the positive predictive value (PPV) of the school nurse's exam? a. 38.7% b. 34.6% c. 37.5% d. 35.6% e. 39.0% 30. A school nurse examined a population of 1,000 children in an attempt to detect nearsightedness. The prevalence of myopia in this population is known to be 15%. The sensitivity of the examination is 60% and its specificity is 80%. All children labeled as "positive" (i.e., suspected of having myopia) by the school nurse are sent for examination by an optometrist. The sensitivity of the optometrist's examination is 98% and its specificity is 90%. How many children will be labeled myopic following the optometrist's exam? a. 105 b. 110 c. 90 d. 120 e. 115 7

Exercise 2 Chapters 4 & 5(2)

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