NR 503 Week 4 Midterm Review Guide

Chapter 1-4 ----------------- 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 10-20 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, non of his classmates had been infected by VZV. The main reason was: 3. Question: The ability of a single person to remain free of clinical illness following exposure to infectious agent is known as: 4. Question: Which of the following is characteristic of single-exposure, common-vehicle outbreak? 5. Question: What is the diarrhea attack rate in persons who ate both ice cream and pizza? 6. Question: What is the OVERALL attack rate in persons who did not eat ice cream? 7. Question: Which of the food items (or combination of items) is most likely to the infective item(s)? 8. Question: Which of the following reasons can explain why a person who did not consume the infective food item got sick? 9. Question: An outbreak of gastroenteritis occurred at a boarding school with a student enrollment of 846. 10. Question: Same question above Calculate the attack rates for boys and girls separately. 11. Question: Same question What is the proportion of total cases occurring in boys? 12. Question: Same question What is the proportion of total cases occurring in students who live in dormitories? 13. Question: Same question Which proportion is more informative for the purpose of the outbreak investigation? 14. Question: A group of researchers are interested in conducting a clinical trial to determine whether a new cholesterol-lowering agent was useful in preventing coronary heart disease (CHD). They identified 12,327 potential participants for the trial. At the initial clinical exam, 309 were discovered to have CHD. The remaining subjects entered the trial and were divided equally into the treatment and placebo groups. Of those in the treatment group, 505 developed CHD after 5 years of follow-up while 477 developed CHD during the same period in the placebo group. What was the prevalence of CHD at the initial exam? 15. Question: Same question What was the incidence of CHD during the 5-year study? 16. Question: Which of the following are examples of 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 calculation assuming that most women who have hysterectomies are older than 50 years of age? 18. Question: A survey was conducted among 1,000 randomly sampled adult males in the United States in 2005. The results from this survey are shown below. 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 researcher’s interpretation: 19. Question: The incidence and prevalence rates of a chronic childhood illness for a specific community are given below. 20. Question: A prevalence survey conducted from January 1 through December 21, 2003 identified 580 new cases of TB in a city of 2 million persons. The incidence rate of TB in this population has historically been 1 per 4,000 persons each year. What is the incident rate of TB per 100,000 persons in 2003? 21. Question: Same info as above, Has the risk of TB 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 36,000. The city has a passive surveillance system that collects hospital and private physician reports of influenza cases every month. During the period between 1/1 and 4/1, 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 4/1. The monthly incidence rate of active cases o influenza for the 3-month period was: 24. Question: Same info The prevalence rate of active influenzas as of 4/ 1/ 05. 25. Question: Same info –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 dease 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: Same info- Which statement is true concerning the duration of the disease after the development of the lab test? 30. Question: Same info- 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 12/31/2005. 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 disease in miners ages 20 to 64 years. The expected number of deaths in this occupational group, based on age-specific death rates for lung disease 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 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: Same info- 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: Same info- 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 following table gives the mean annual age-specific mortality rates from measles during the first 25 years of life in successive 5-year periods. You may assume that the population is in a steady state (migrations out are equal to migrations in). The age specific mortality rates for the cohort born in are: 38. Question: Same info- based on the information above, one may conclude: 39. Question: Which of the following characteristics indicate the mortality rates provide a reliable estimate of disease incidence? More than one answer may be correct. 40. Question: Which of the following statement are true? More than one answer may be correct. 1. A mortality rate can approximate an incidence rate under conditions of a high case-fatality rate and a short duration of disease. 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 date 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. The case-fatality rate associated with plague is lowest in which community? 45. Question: Same info- The proportionate mortality ratio associated with plague is lowest in which community? Chapter 5-6 ---------------- 1. Question: In a community-based hypertension testing program called HT-Aware, the detection level for high blood pressure is set at 140mmHg for systolic blood pressure. A separate testing program called HT-Warning in the same community sets the level at 130mmHg 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: Same info- What is the positive predictive value (PPV) of the school nurses’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. What is the sensitivity of the PSA screening test in the combined groups? 12. Question: Same info- 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. 17. Question: What is the estimate of kappa for the reliability of the two doctors’ test results? 17. Question: This table represents the results of coronary magnetic resonance (CMR) angiography compared to x-ray angiography (the gold standard in diagnosis of coronary artery disease) in a high-risk population of patients scheduled to undergo x-ray angiography for suspected coronary artery disease. 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? 18. 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, 19. 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. What was the annual mortality rate for the country during 2005? 20. 22. Question: Assume that the population remained constant throughout the year. What was the case-fatality rate (CFR) from TB during 2005? 21. 23. Question: What is the proportionate mortality ratio (PMR) for TB during 2005? 22. The PMR is the number of deaths due to a specific cause divided by all deaths. In this example, the PMR equals 45,000 TB deaths divided by 175,000 deaths, or approximately 23. Question: Not all 135,000 cases of TB were contracted during 2005. Which of the following statements is true? 24. Question: Which of the following statements pertains to relative survival? 25. Question: What was the probability of surviving the second year given survival to the end of the first year? 26. Question: What was the cumulative probability of surviving after only 2 years of follow-up? 27. Question: An important assumption in this type of analysis is that: 28. Question: Tables not included 29. Question: Tables not included 30. Question: Which of the following is a key assumption involved in the use of life-table analysis? 31. Question: Which of the following is a measure of disease prognosis? 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. What is the overall case-fatality rate for the worldwide epidemic of SARS? 33. Question: Based on the table, we can conclude that the case-fatality rate (CFR) in Vietnam: 34. Question: Following a revision in the case definition, more persons were found to have suffered from an infection with the SARS virus. The inclusion of these cases, almost all asymptomatic, did not impact the total number of SARS fatalities. What happened to the case-fatality rate (CFR) following this reclassification? 35. Question: What is the probability of surviving the second year of the study given that a person survived the first year? 36. Question: Table not avb 37. Question: What is the probability chance of surviving 3 years after diagnosis? 38. The cumulative survival probability for all 3 years equals the product of the independent interval survival probabilities. In this example, 59% multiplied by 53% multiplied by 70.4% gives a cumulative survival probability of 22%. 39. Question: Table not avb 40. 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: Chapter 7-8 1. Question: Which of the following statements best describe efficacy? 2. Question: A study is conducted for a pharmaceutical agent that has shown promise for reducing heart disease among women. In order to more fully test the agent, an additional study is done restricting the participants to be randomized to those who have a history of hypertension. Which of the following advantages cannot be claimed by the researchers? 3. Question: A new drug treatment for cardiac thrombus claims to have a higher success rate than the current drug. A strong sign of the potential success is the lack of internal hemorrhaging starting 2 days after treatment. 168 patients who require treatment for cardiac thrombi are randomized after agreeing to participate in a trial of the new drug. The researchers were interested in whether the new drug reduced the need for blood transfusions due to internal hemorrhage compared to the current treatment. The following table summarizes the results of her study: What is the incidence of needing a blood transfusion in the group of persons who were randomized to the new drug treatment? 4. Question: Same table info- What is the number of persons who died in hospital in the study? 5. Question: Same table- What is the main advantage of the randomization of the 168 study participants to one of the two drug treatment groups? 6. Question: The researchers interpret the findings to conclude that the new drug treatment is more likely to result in a blood transfusion and subsequent death. This statement is: 1. Though the death rate among those receiving a transfusion cannot be directly compared with this table, the high rate of transfusion and subsequent death in the new drug treatment group strongly implies that the new drug treatment is more likely to result in these outcomes. 7. Question: A randomized, double-blind clinical trial of a varicella vaccine observed an estimated incidence of 25% chickenpox episodes in persons receiving the vaccine, compared to 80% among persons receiving a placebo. The estimated efficacy of the vaccine is: 8. Question: A multicenter double-blind randomized study was carried out to compare the effect of drug X with that of a placebo in patients surviving acute myocardial infarction (AMI). Treatment with the drug started 7 days after infarction in 1,884 patients, 52% of all persons who were evaluated for entry into the study. 945 participants were randomized to treatment with drug X while 939 were assigned to the placebo group. Patients were then followed for 12 months for reinfarction. There were 152 deaths in the placebo group and 98 in the group receiving drug X. After entry into the study, patients were first classified into three groups, those who had a previous AMI, those with a first AMI who were at high risk for other cardiovascular diseases such as congestive heart failure, and those with a first AMI who were at low risk for other cardiovascular diseases. Which term best describes the study design? 9. Question: After assignment to treatment group, 77% of those in the placebo group were men, while 80% of those in the drug X group were men. Which statement is most likely to be true? 10. Question: A preliminary analysis was conducted after 6 months and found that 87% of participants in the placebo group and 85% of those in the drug X group had taken more than 90% of their prescribed dosages. Which statement best describes this finding? 11. Question: Which of the following statements best describes the reason for conducting the study as a double-blind trial? 12. Question: The researchers conclude that treatment with drug X reduces mortality in patients who have had an AMI. The researchers are: 13. Question: The following data come from a study of approaches to smoking cessation. Smokers who want to quit were randomized to one of four groups: control group C who received no intervention assistance, quitting guide group Q who received brochures about how to quit smoking, quitting guide and support group QS who received quitting brochures as well as social support brochures listing benefits of smoking cessation, and telephone support group T who received the brochures and a monthly phone call from a counselor. Participants received mailed surveys at 8, 16, and 24 months after randomization. The results after 2 years are in the table below. What is the overall quit rate after 2 years of follow-up? 14. Question: same info- Which group had the least success in terms of quitting smoking? 15. Question: same info- What is the main purpose of randomization in this study? Chapter 9-15 ----------------- 1. Question: A study is planned to investigate the relationship of factors associated with maternal hypertension and the risk of congenital birth defects in children born to these women. Which of the following would be a reason for using a cohort study design? 2. Question: A researcher is interested in the etiology of myocardial infarction (MI) among men between 18 and 40 years of age. Her hypothesis concerns the influence of diets high in fat and subsequent development of MI. What is the best study approach to address this hypothesis? 3. Question: Which of the following is an advantage to the conduct of a cohort study? 4. Question: A cohort study is planned to investigate the potential adverse health effects of daily alcohol consumption. In assessing the risk of liver cancer related to alcoholism, which of the following is not an important methodologic consideration? 5. Question: Which of the following is not an advantage of a retrospective cohort study? 6. Question: In a study of the adverse effects of x-rays among children, a retrospective cohort study was done using records from several large children’s hospitals for the period of 1980 to 1985. 10,000 children were selected as a representative population of ill children seen at the hospitals during that time. Subjects were classified according to whether or not they received an x-ray during their stay in the hospital and were followed from their hospital stay through 2005 for the development of cancer. During the follow-up period, 49 incident cancers occurred in 3,263 children who had received an x-ray during their hospitalization. In this retrospective study, which of the following groups are eligible for selection into the study? 7. Question: In a study of the adverse effects of x-rays among children, a retrospective cohort study was done using records from several large children’s hospitals for the period of 1980 to 1985. 10,000 children were selected as a representative population of ill children seen at the hospitals during that time. Subjects were classified according to whether or not they received an x-ray during their stay in the hospital and were followed from their hospital stay through 2005 for the development of cancer. During the follow-up period, 49 incident cancers occurred in 3,263 children who had received an x-ray, and 47 incident cancers occurred in the 6,737 children who had not received an x-ray during their hospitalization. What are the rates of cancer incidence in each exposure group? 8. Question: Same info as above. What is the attributable risk of cancer due to x-ray in this study population? What is the interpretation of this estimate? 9. Question: Same info as above. What is the risk ratio for the effect of exposure on the development of cancer in this study? What is the interpretation of this estimated ratio? 10. Question: Same info as above. Which of the following issues should the investigators consider when interpreting whether a causal association exists between cancer incidence and childhood x-ray? 11. Question: Which of the following may be a factor that would result from the inability to use randomization in a cohort study? 12. 6,750 people who were free of disease X were enrolled in a cohort study in 1985 and followed with annual exams and interviews through 1995. Exposure to factor A was determined at study enrollment and the participants were followed until 1995 to observe new cases of disease X. Data from the study at the end of follow-up are shown in the following table. What is the incidence rate of disease X among persons exposed to factor A? 13. Question: What is the relative risk for the effect of exposure to factor A on disease X? 14. Question: In 2002, investigators started a study of the association of cholesterol levels and stroke in a group of 2,000 healthy persons who had participated in a cholesterol screening program in 1992. The investigators determined exposure categories using cholesterol levels in all persons that were measured at the time of the screening program. A cutoff value of 200 mg/dL was used to define “high” cholesterol while those with levels below 200 were identified as having “low” cholesterol. Using this definition, 1,000 persons had “high” cholesterol levels while the remaining 1,000 persons had “low” cholesterol. The investigators determined that 150 cases of stroke occurred by the end of 2004, with 113 cases occurring in the high cholesterol group. What is the study design that the investigators used? 15. Question: Same info as above. What type of risk measure should the investigators calculate? 16. Question: same info as above. Using the reported study data, what is the estimate of the risk measure that was chosen? 17. Question: What is a necessary assumption for the study’s findings to be true? 18. Question: The following data are from a prospective study that examined the relationship between smoking and incidence of both myocardial infarction (heart attack) and breast cancer among women. What is the proportion attributable risk of breast cancer among smokers? 19. Question: same info. What is the relative risk of myocardial infarction for smokers? 20. same info. If the proportion of smokers in this population is 30%, what is the population proportion attributable risk of breast cancer due to smoking? 21. Question: A researcher is interested in the etiology of cervical cancer among women between 18 and 35 years of age. Her hypothesis concerns the influence of sexually transmitted diseases such as human papilloma virus (HPV) and subsequent development of cancer. What is the best study approach to address this hypothesis? 22. Question: Suppose that 350 cervical cancer cases were identified and a random sample of women of the same age range who were admitted to the hospital included 500 eligible controls. After independent blood tests of all cases and controls, 90% of cases were positive for HPV antibodies while 63% of controls were positive for antibodies to the virus. What is the appropriate ratio measure of association and its value? 23. Question: Suppose that one third of all cervical cancer cases were smokers as were one third of all controls and smoking status is independent of HPV infection. Is smoking a potential confounder in this study? 24. Question: A case-control study was conducted to determine if an association exists between workers in uranium mines and loss of fertility due to reduced sperm count. A group of 200 men with low sperm count were identified from clinics located in areas with uranium mines. Each selected case was matched with a randomly selected male control on the following factors: race, age, area of residence, and smoking status. What is the purpose of matching? 25. Question: The following numbers of matched pairs were reported: 4 matched pairs in which both men worked in a uranium mine, 9 pairs in which the case had mine exposure but the control did not, 2 pairs in which the case had no mine exposure but the control did, and 185 pairs in which neither man had worked in a uranium mine. What is the odds ratio for reduced sperm count among the uranium miners? 26. Question: (A table not provided) A case-control study of the relationship between high-fat diet and diabetes was performed. The results of the study are shown below, stratified by gender. What is the crude odds ratio for the association between high-fat diet and diabetes in this study? 27. Question: same info. What is the odds ratio among men only? 28. Question: same info as above. What is the odds ratio among women only? 29. Question: same info. Based on the responses above, what is the most appropriate measure of association to present when reporting the results of this study? 30. Question: same info. Which of the following is demonstrated by the stratified odds ratio shown above? 31. Question: When incidence density sampling is used in a case-control study, which of the following is an important consideration? 32. Question: A recent prospective study on baldness and coronary heart disease (CHD) concluded that there was no association between the two, despite earlier cross-sectional studies which showed that baldness was associated with CHD when the two were determined at the same time in men. Which Bradford-Hill criterion is being tested by the newer study? 33. Question: A study examined the relation between use of estrogen replacement therapy (ERT) and ovarian cancer mortality using a prospective design. Of 24,231 eligible women, none had a prior history of cancer, hysterectomy, or ovarian surgery at enrollment in 1982. During 12 years of follow-up, 44 deaths from ovarian cancer occurred. In the published results, the authors note that 12,543 were excluded from the original cohort due to missing information for prior history variables. Which of the following is of greatest concern when interpreting the study results? 34. Question: Same info as question 33. Age at menopause is a potential factor associated with use of ERT. The study investigators created three categories for age at menopause: less than 45 years, 46 through 54 years, and 55 years or more. After stratifying on age at menopause, the researchers reported relative risks of 0.97, 1.00 (referent), and 0.93 for each age group, respectively. Which of the following is true? 35. Question: A case-control study was conducted to assess whether occupational radiation exposure among men was associated with Down syndrome in their children. The investigators matched cases and controls on age of the mother at childbirth by 5-year categories. Why was this done? 36. Question: Same info as above. When possible, information on paternal radiation exposure was taken from employment records rather than from subject interviews. Why was this done? 37. Question: An epidemiologist was interested in determining whether aspirin was associated with an increased risk of gastrointestinal (GI) bleeding. She relied on primary physicians to identify 600 patients at a hospital who were taking a daily dose of aspirin and 600 other patients who were not taking aspirin. Subjects were followed for 1 year to detect any occurrences of GI bleeding. Due to publicity about the risk of bleeding associated with aspirin, primary physicians treating patients at the hospital followed their patients who were taking aspirin more closely than they were unexposed subjects. Which of the following describes the impact that this may have on the epidemiologist’s study? 38. Question: same info from question 37. Suppose that the study was repeated with a second physician who was responsible for verifying a diagnosis of GI bleeding in the patients. This physician was informed that all patients were using aspirin. If the likelihood of diagnosing the outcome among unexposed subjects was increased while all other diagnostic probabilities remained the same, what impact would this have on the bias? 39. Question: Matching is employed in a case-control study in order to ensure that: 40. Question: The effect of exposure to high-density automobile traffic either as a bicyclist or pedestrian was compared to minimal or no exposure to automobile traffic. It is hypothesized that direct exposure to automobile traffic has an effect on acute myocardial infarction (MI). This association was studied with 500 incident cases of MI diagnosed in the emergency rooms of several hospitals and compared to 1,000 other subjects who visited the same emergency rooms for reasons other than cardiovascular and respiratory diseases. All subjects were asked to report the amount of time that they spent exposed to high-density traffic over the past month prior to their hospital visit. What type of study design is this 41. Question: same info as question 40. After completing the recruitment, the investigators compiled their data in the following table: Using the appropriate measure of association, as compared to the group with no traffic exposure, which of the following is a true statement concerning MI? 42. Question: same info as above. Which of the following may explain the reason for the observed association? 43. Question: Which of the following is an advantage of the case-control study design? 44. Question: A large case-control study using multiple recruitment centers was conducted comparing 2,987 lung smoker cases to 3,013 other hospitalized persons selected as controls. One objective was to study the association between occupational exposure to chemicals and lung cancer. After compiling the data, the investigators noted that 90% of persons with lung cancer were smokers while 67% of the controls were smokers. The most practical and efficient way to eliminate differences between the cases and controls with regard to smoking would be to: 45. Question: An investigator is interested in studying the adverse effects of exposure to toxic metals on neurologic diseases such as Alzheimer’s disease. In assessing this risk, all of the following are important considerations for a prospective study design except: 46. Question: A history of dietary supplement with calcium was recorded among 10,000 women over the age of 50. The women were followed for 2 years to determine if they experienced hip fracture. Calcium supplementation was reported by 31% of women who experienced hip fracture and by 46% of all other women. In a case-control study with equal numbers of cases and controls, what is the number of women with a hip fracture who are not taking calcium supplements? 47. Question: same info as above. What are the odds of a hip fracture among women who are taking calcium supplements 48. Question: same info as above. What is the measure of association between calcium supplementation? 49. Question: In a study of 100 cases of colon cancer in women, there were 200 age- and race-matched controls. The suspected etiologic factor was higher-than-average consumption of red meat. The absolute risk of colon cancer in persons with this level of consumption is: 50. Question: Why are controls needed in a case-control study? 51. Question: When is odds ratio obtained in a case-control study a reliable approximation of the relative risk for the general population? 52. Question: In a published epidemiologic study investigating infertility related to sexually transmitted diseases (STD), the authors state that 5% of identified cases refused enrollment, 10% of identified cases were lost to follow-up prior to data collection, and 10% of interviewed cases had missing data for one or more key variables describing exposure. Based on this information, which of the following statements is most likely to be true? 53. Question: same info as question 52. After data were gathered for the study, the investigators decided to restrict the analysis to women only, rather than including both men and women in the study. Assuming that sex is a confounder of the exposure–disease relationship under investigation, this decision would have which of the following effects? 54. Question: same info. In the primary analysis of the study, the investigators measured exposure as a dichotomous variable (any history of STD compared to no history of STD). In subsequent analyses, the investigators looked at the relationship between specific STDs and infertility. They noted the following measures of association: for past history of gonorrhea, the odds ratio was 2.4 with a 95% confidence interval of 1.3 to 4.4. For past history of chlamydia, the odds ratio was 1.8 with a 95% confidence interval from 1.2 to 2.1. These results indicate that: 55. Question: If an investigator is analyzing the results of a clinical trial, then applying the “intention to treat” rule means that which type of bias is most likely to result? 56. Question: Investigators wanted to know if some military personnel are more error prone than others and would be a poor risk for training as a pilot. A study was done in which individuals who had injuries during basic training were compared to individuals who had not had an injury during training. Both groups were asked to recall episodes during childhood when they had had accidents that resulted in an injury. The individuals with a training injury reported more incidents during childhood when they had an injury. Therefore, the military command concluded that some persons are more likely to be error prone and that individuals with a childhood injury should be excluded from pilot training. One commanding officer disagreed with this conclusion. He asked the investigators to design a second study in which all individuals were asked about childhood injuries prior to the start of basic training. The group who reported having a childhood injury was compared to the group who had not had a childhood injury to determine which group had a higher rate of injuries during basic training. At the end of follow-up, there was no difference in the rate of injuries experienced by each group. What type of design was used for the first study? 57. Question: same info as question 56. What type of study design was used for the second study? 58. Question: same info as above. Which study better tests the hypothesis that there is a relationship between childhood injury and subsequent injury during basic training? 59. Question: same info as above. Which of the following may explain why the two studies observed different results concerning the association between childhood injury and training injury? - 60. Question: In a study of oral contraceptive (OC) use and hypertension, male interviewers for the study found a lower prevalence of OC use among participants than did female interviewers using the same questionnaire. Which term best describes this finding? 61. Question: A matched case-control study of sunscreen use during childhood and melanoma results in an odds ratio of 1.0. Cases of melanoma were matched by sex and race to controls who were identified by random digit dialing. What is the most likely explanation for the study’s null finding? 62. Question: Among patients with liver cancer, current alcohol drinkers have a worse prognosis for survival than nondrinkers. What would be the impact on the odds ratio for a case-control study of current alcohol use and liver cancer mortality if prevalent cases were included with incident cases of the cancer? 63. Question: In a cohort study, the reported relative risk was 2.0; however, the investigators concluded that the study likely had a bias away from the null hypothesis, but they concluded that an association did exist between the exposure and the outcome. The true relative risk is most likely: 64. Question: In a case-control study of maternal cigarette smoking as a risk factor for low birth weight, the investigators concluded that mothers of children with low birth weight were more likely to report smoking during pregnancy relative to mothers of children with normal birth weight. The reporting error most likely caused the odds ratio to: 65. Question: In a case-control study of obesity and adult-onset asthma, controls are matched to cases on the basis of race and gender. This approach to selection is intended to decrease the influence of which type of bias? 66. Question: In a case-control study of computer display exposure and glaucoma, cases and controls were also asked about television watching habits. Errors in recall of exposure to video screens occurred with equal frequency among cases and controls. Which one of the following biases likely occurred? 67. Question: same info as above. What is the most likely effect of this bias on the measure of association reported by the study? 68. Question: same info as above. Which of the following methods for adjusting for confounding by age is most likely to affect the generalizability of the study findings? 69. Question: In a cohort study of occupational exposure to a chemical and subsequent incidence of bladder cancer, all workers who smoked were more likely to die of other causes before bladder cancer was diagnosed. What was the effect of this premature mortality on the measure of association reported by the study? 70. Question: Which of the following statements about person-years is not true? Chapter 16-20 --------------------- 1. Question: A large company institutes a new wellness program aimed at improving the health of its 50,000 employees. As a part of the program, all employees are given physical examinations and screening tests. One of the tests given to male employees is the prostate specific antigen (PSA) test with all employees testing positive being referred to their private physician for a thorough examination involving the standard test, a digital rectal examination (DRE). What will happen to the apparent incidence rate of prostate cancer in the company during the first year of this program