Chapters 2-4

1. Question: Which of the following is a condition which may occur during the incubation period?
2. Question: Chicken pox is a highly communicable disease. It may be transmitted by direct contact with a person infected with the varicella-zoster virus (VZV). The typical incubation time is between 10 to 20 days. A boy started school 2 weeks after showing symptoms of chicken pox including mild fever, skin rash, and fluid-filled blisters. One month after the boy returned to school, none of his classmates had been infected by VZV. The main reason was:
3. Question: Which of the following is characteristic of a single-exposure, common-vehicle outbreak?
4. Question: What is the diarrhea attack rate in persons who ate both ice cream and pizza?
5. Question: What is the overall attack rate in persons who did not eat ice cream?
6. Question: Which of the food items (or combination of items) is most likely to be the infective item(s)?
7. Question: Which of the following reasons can explain why a person who did not consume the infective food item got sick?
8. Question: An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of 846. Fifty-seven students reported symptoms including vomiting, diarrhea, nausea, and low-grade fever between 10 p.m. on September 24 and 8 p.m. on September 25. The ill students lived in dormitories that housed 723 of the students. The table below provides information on the number of students per type of residence and the number reporting illnesses consistent with the described symptoms and onset time. Calculate the attack rate among all students at the boarding school.
9. Question: Calculate the attack rate among all students at the boarding school.
10. Question: Calculate the attack rates for boys and girls separately.
11. Question: What is the proportion of total cases occurring in boys?
12. Question: What is the proportion of total cases occurring in students who live in dormitories?
13. Question: Which proportion is more informative for the purpose of the outbreak investigation?
14. Question: What was the prevalence of CHD at the initial exam?
15. Question: What was the incidence of CHD during the 5-year study?
16. Question: Which of the following are examples of a population prevalence rate?
17. Question: What would be the effect on age-specific incidence rates of uterine cancer if women with hysterectomies were excluded from the denominator of incidence calculations assuming that most women who have had hysterectomies are older than 50 years of age.
18. Question: The researchers stated that there was a doubling of risk of hypertension in each age group younger than 60 years of age. You conclude that the researchers’ interpretation:
19. Question: The incidence and prevalence rates of a chronic childhood illness for a specific community are given below. Based on the data, which of the following interpretations best describes disease X?
20. Question: What is the incident rate of tuberculosis per 100,000 persons in 2003?
21. Question: Has the risk of tuberculosis increased or decreased during 2003?
22. Question: Which of the following is an advantage of active surveillance?
23. Question: The population of a city on February 15, 2005, was 36,600. The city has a passive surveillance system that collects hospital and private physician reports of influenza cases every month. During the period between January 1 and April 1, 2005, 2,200 new cases of influenza occurred in the city. Of these cases, 775 persons were ill with influenza according to surveillance reports on April 1, 2005. The monthly incidence rate of active cases of influenza for the 3-month period was:
24. Question: The prevalence rate of active influenza as of April 1, 2005, was:
25. Question: What can be inferred about influenza cases occurring in the city?
26. Question: A study found that adults older than age 50 had a higher prevalence of pneumonia than those who were younger than age 50. Which of the following is consistent with this finding?
27. Question: Which of the following statements are true? More than one answer may be correct.
28. Question: A disease has an incidence of 10 per 1,000 persons per year, and 80% of those affected will die within 1 year. Prior to the year 2000, only 50% of cases of the disease were detected by physician diagnosis prior to death. In the year 2000, a lab test was developed that identified 90% of cases an average of 6 months prior to symptom onset; however, the prognosis did not improve after diagnosis. Comparing the epidemiology of the disease prior to 2000 with the epidemiology of the disease after the development of the lab test, which statement is true concerning the disease in 2000?
29. Question: Which statement is true concerning the duration of the disease after the development of the lab test?
30. Question: Which statement is true concerning the disease-specific mortality rate after the development of the lab test?
31. Question: In a coastal area of a country in which a tsunami struck, there were 100,000 deaths in a population of 2.4 million for the year ending December 31, 2005. What was the all-cause crude mortality rate per 1,000 persons during 2005?
32. Question: In an industrialized nation, there were 192 deaths due to lung diseases in miners ages 20 to 64 years. The expected number of deaths in this occupational group, based on age-specific death rates for lung diseases in all males ages 20 to 64 years, was 238 during 1990. What was the standardized mortality ratio (SMR) for lung diseases in miners?
33. Question: In 2001, a state enacted a law that required the use of safety seats for all children under 7 years of age and mandatory seatbelt use for all persons. The table below lists the number of deaths due to motor vehicle accidents (MVAs) and the total population by age in 2000 (before the law) and in 2005 (4 years after the law was enacted).  What is the age-specific mortality rate due to MVAs for children ages 0 to 18 years in 2000?
34. Question: Using the pooled total of the 2000 and 2005 populations as the standard rate, calculate the age-adjusted mortality rate due to MVAs in 2005.
35. Question: Based on the information in the table, it was reported that there was an increased risk of death due to MVAs in the state after the law was passed. These conclusions are:
36. Question: For colorectal cancer diagnosed at an early stage, the disease can have 5-year survival rates of greater than 80%. Which answer best describes early stage colorectal cancer?
37. Question: The age-specific mortality rates for the cohort born in 1915-1919 are:
38. Question: Based on the information above, one may conclude:
39. Question: Which of the following characteristics indicate that mortality rates provide a reliable estimate of disease incidence? More than one answer may be correct.
40. Question: Which of the following statements are true? More than one answer may be correct.
41. Question: Among those who are 25 years of age, those who have been driving less than 5 years had 13,700 motor vehicle accidents in 1 year, while those who had been driving for more than 5 years had 21,680 motor vehicle accidents during the same time period. It was concluded from these data that 25-year-olds with more driving experience have increased accidents compared to those who started driving later. This conclusion is:
42. Question: For a disease such as liver cancer, which is highly fatal and of short duration, which of the following statements is true? Choose the best answer.
43. Question: The prevalence rate of a disease is two times greater in women than in men, but the incidence rates are the same in men and women. Which of the following statements may explain this situation?
44. Question: The table below describes the number of illnesses and deaths caused by plague in four communities.
45. Question: The table below describes the number of illnesses and deaths caused by plague in four communities.  The proportionate mortality ratio associated with plague is lowest in which community?

Chapters 5-6

1. Question: 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?
2. Question: 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?
3. Question: What is the positive predictive value (PPV) of the school nurse’s exam?
4. Question: How many children will be labeled myopic following the optometrist’s exam?
5. Question: What is the positive predictive value (PPV) of the optometrist’s exam?
6. Question: What is the negative predictive value (NPV) of the optometrist’s exam?
7. Question: What is the overall sensitivity of the sequential examinations?
8. Question: What is the overall specificity of the sequential examinations?
9. Question: What would be the positive predictive value (PPV) of the exam for myopia if the optometrist tested all 1,000 children?
10. Question: Which of the following improves the reliability of diabetes screening tests?
11. Question: A prostate specific antigen (PSA) test is a quick screening test for prostate cancer. A researcher wants to evaluate it using two groups. Group A consists of 1,500 men who had biopsy-proven adenocarcinoma of the prostate while group B consists of 3,000 age- and race-matched men all of whom showed no cancer at biopsy. The results of the PSA screening test in each group is shown in the table.
12. Question: What is the specificity of the screening test in the combined groups?
13. Question: What is the positive predictive value (PPV) of the screening test in the combined groups?
14. Question: The PSA screening test is used in the same way in two equal-sized populations of men living in different areas of the United States, but the proportion of false positives among those who have a positive PSA test in the first population is lower than that among those who have a positive PSA test in the second population. What is the likely explanation for this finding?
15. Question: Test A has a sensitivity of 95% and a specificity of 90%. Test B has a sensitivity of 80% and a specificity of 98%. In a community of 10,000 people with 5% prevalence of the disease, Test A has always been given before Test B. What is the best reason for changing the order of the tests?
16. Question: Two neurologists, Drs. J and K, independently examined 70 magnetic resonance images (MRIs) for evidence of brain tumors. As shown in the table below, the neurologists read each MRI as either “positive” or “negative” for brain tumors. Based on the above information, the overall percent agreement between the two doctors including all observations is:
17. Question: What is the estimate of kappa for the reliability of the two doctors’ test results?
18. Question: In the general population, the prevalence of coronary artery disease is apporximately 6%. Assuming that this sample of patients is representative of the general population, the sensitivity of the CMR test in the general population would be approximately:
19. Question: After reviewing the results of the test comparison, an epidemiologist decides that the specificity of the test is too low. Using the same CMR images, he raises the cutoff value for a positive test to increase the specificity. What is the likely effect on the sensitivity?
20. Question: In comparing the mammography readings of two technicians who evaluated the same set of 600 mammograms for presence of breast cancer from a generally representative sample of women from the population,
21. Question: In a country with a population of 16 million people, 175,000 deaths occurred during the year ending December 31, 2005. These included 45,000 deaths from tuberculosis (TB) in 135,000 persons who were sick with TB. Assume that the population remained constant throughout the year.
22. Question: In a country with a population of 16 million people, 175,000 deaths occurred during the year ending December 31, 2005. These included 45,000 deaths from tuberculosis (TB) in 135,000 persons who were sick with TB. Assume that the population remained constant throughout the year. Not all 135,000 cases of TB were contracted during 2005. Which of the following statements is true?
23. Question: Which of the following statements pertains to relative survival?
24. Question: What was the probability of surviving the second year given survival to the end of the first year?
25. Question: What was the cumulative probability of surviving after only 2 years of follow-up?
26. Question: An important assumption in this type of analysis is that:
27. Question: Complete the table. What is the probability that a person enrolled in the study will survive to the end of the third year?
28. Question: Before reporting the results of this survival analysis, the investigators compared baseline characteristics of the 38 people who withdrew from the study before its end to those who had complete follow-up. This was done for which of the following reasons:
29. Question: Which of the following is a key assumption involved in the use of life-table analysis?
30. Question: Which of the following is a measure of disease prognosis?
31. Question: In 2003, Sudden Acute Respiratory Syndrome (SARS) appeared in several countries, mainly in Asia. The disease was determined to have been caused by a virus that could be spread from person –to person from the index case occurring in mainland China. This table reflects the total number of reported cases of SARS and deaths among those cases as best as can be determined. What is the overall case-fatality rate for the worldwide epidemic of SARS?
32. Question: In 2003, Sudden Acute Respiratory Syndrome (SARS) appeared in several countries, mainly in Asia. The disease was determined to have been caused by a virus that could be spread from person –to person from the index case occurring in mainland China. This table reflects the total number of reported cases of SARS and deaths among those cases as best as can be determined. Based on the table, we can conclude that the case-fatality rate (CFR) in Vietnam:
33. Question: What happened to the case-fatality rate (CFR) following this reclassification?
34. Question: What is the probability of surviving the second year of the study given that a person survived the first year?
35. Question: For all people in the study, what is the probability of surviving to the end of the second year?
36. Question: What is the probability chance of surviving 3 years after diagnosis?
37. Question: What is the total number of person-years of follow-up for patients in the study assuming a median survival time of one half of the year for all persons dying during an interval and an observation time of one half of the year for all persons withdrawing from the study?
38. Question: Before reporting the results of this survival analysis, the investigators compared baseline characteristics of the 44 people who withdrew from the study before its end to those who had complete follow-up. This was done: