Concept Checks

Malaria is a parasitic disease transmitted by the Anopheles mosquito bite. This mode of transmission is called

vector.

The following information summarizes the exercise status and obesity status in a case-control study. What are the odds of regular exercise in the obesity group?

0.16 The number of regular exercise in the obesity group is 7, and the number of no exercise in the same group is 43. Therefore the odds of exercise in the obesity group is 0.16 (7 divided by 43).

Epidemiologists decided to investigate the effect of sunscreens on sunburns. They ran an epidemiologic study to see the association of sunscreens and sunburns. Overall, 460 people have enrolled in the study. Investigators randomly allocated 230 people to the treatment group (sunscreens) and 230 to the control group (placebo). They exposed those 460 people to the high mountain trail on a sunny day. At the end of the study, 30 people developed sunburns in the sunscreen group and 130 people developed sunburns in the placebo group. What is the relative risk of sunburns in the sunscreen treatment group compared with the control group in this study?

0.23 The risk of sunburns in the exposure group is 30 divided by 230 (0.13), and the risk of sunburns in the placebo group is 130 divided by 230 (0.57). The relative risk is 0.23 (0.1 divided by 0.57).

The following information summarizes the exercise status and obesity status in a case-control study. What is the odds ratio of regular exercise in this study?

0.44 The odds of exercise in the obesity group is 7 divided by 43 (0.163), and the odds of exercise in the non-obesity group is 27 divided by 73 (0.370). The odds ratio is 0.44 (0.163 divided by 0.370).

The following table summarizes the findings of a cohort study. Participants were enrolled in January 1, 2015, and followed up until December 31, 2015. Researchers were interested in the effect of physical activity on cardiovascular disease. Based on the previous information, calculate the relative risk of cardiovascular events for those who were physically active

0.56 The risk for active participants is 14/1,000 per year, and the risk for inactive is 25/1,000 per year. Thus the relative risk is calculated as follows: (14/1,000)/(25/1,000) = 0.56.

Epidemiologists decided to investigate the effect of sunscreens on sunburns. They ran an epidemiologic study to see the association of sunscreens and sunburns. Overall, 460 people have enrolled in the study. Investigators randomly allocated 230 people to the treatment group (sunscreens) and 230 to the control group (placebo). They exposed those 460 people to the high mountain trail on a sunny day. At the end of the study, 30 people developed sunburns in the sunscreen group and 130 people developed sunburns in the placebo group. What is the risk of developing sunburns in the placebo group?

0.57 The population at risk in the placebo group is 230, and the number of positive outcomes (sunburns) in the placebo group is 130. Therefore the risk of developing sunburns in the placebo group is 0.57 (130 divided by 230).

Unmatch the pairs. What are the estimated odds of exposure in controls when analyzing this study as an unmatched case-control study design?

0.67 The odds of exposure among controls is found by dividing the number of exposed people among controls (6) by 9 (the number of unexposed people among controls), which equals 0.67.

There was a food poisoning outbreak on April 1, 2022, at the City Z Food Safety Conference. There were 1,000 people registered for the conference with luncheon, 100 volunteers to host attendees, and 50 people who served the luncheon during the conference. Except for 50 people who served the food, all of the participants and volunteers ate the food from the luncheon at the conference on April 1, 2022. Based only on the information given in this question, how many people are at risk in this food poisoning outbreak?

1,100

An epidemiologist decides to investigate the incidence of diabetes in a population of 300 older adults who live in a nursing home. She visits the nursing home in January 1, 2017 and later in December 31 of the same year. She looks into the records of these patients and learns that in her first visit, 25 patients had diabetes and 35 in her second visit. What number should be in the numerator for her calculation of incidence?

10 These 10 people represent the new cases of diabetes, because at the beginning there were already 25 diabetics

What is the attack rate (case-fatality rate) from influenza during the 2016 season in the young age group at Minas Tirith?

10 % Attack rate equals number of deaths divided by number of diagnosed cases. There are 300 deaths and 3,000 diagnosed cases in the young age group. The attack rate is 0.1 (10%),

What is the age-specific mortality rate from disease X in City B for age younger than 65?

10 Deaths/1000 People The age-specific mortality rate of City B for age younger than 65 equals the number of deaths for age younger than 65 divided by the number of individuals at risk for age younger than 65. There are 60 deaths for age younger than 65 in City A, and its population is 6,000 people for age younger than 65. The age-specific mortality rate of City B for age younger than 65 is 10 deaths/1,000 people.

The population of Oriol City in June 2018 was 612,437. According to the Oriol City's health department, there were 329 new cases of Raven's disease during 2018. Counting those new cases, by December 31 it was estimated that there were 6580 persons with Raven's disease in Oriol City. What was the prevalence of Raven's disease in 2018?

1074 per 100,000 population

The following table summarizes the findings of a cohort study. Participants were enrolled in January 1, 2015, and followed up until December 31, 2015. Based on the previous information, calculate the incidence per 1,000 per year of cardiovascular events among those who were categorized as physically active.

14/1,000 per year Incidence in that group is calculated by dividing the number of events over the total number of participants in that group (28/2,000 = 0.014).

What is the incidence rate from influenza in 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

150 cases/1,000 people is the death rate from influenza in the young age group. The incidence rate equals the number of diagnosed cases divided by the number of people at risk. There are 3,000 diagnosed cases in the young age group, and its population is 20,000 people.

What is the estimated odds ratio of cases when analyzing this study as a matched case-control study design?

2.00 The number of exposed pairs is 3, the number of exposed-case and unexposed-control pairs is 6, the number of unexposed-case and exposed-control pairs is 3, and the number of unexposed pairs is 3. Therefore the odds ratio from matched case-control study is (number of exposed-case and unexposed-control pair) divided by (number of unexposed-case and exposed-control pair); 6 divided by 3 equals 2.

Unmatch the pairs. What is the estimated odds ratio of cases when analyzing this study as an unmatched case-control study design?

2.25 The odds ratio of exposure among controls is found by dividing 1.5 (the odds of exposed people among cases) by the odds of exposed people among controls (2 over 3, which equals 2.25).

There was a food poisoning outbreak on April 1, 2018, at the City Z Food Safety Conference. There were 1,000 people registered for the conference with luncheon, 100 volunteers to host attendees, and 50 people who served the luncheon during the conference. Except for 50 people who served the food, all of the participants and volunteers ate the food from the luncheon at the conference on April 1, 2018. After an initial outbreak of food poisoning is reported, an epidemiologist sends surveys to all people at risk to investigate the cause. However, only 900 people among those at risk answer the survey. After analysis of 900 survey results, the epidemiologist concludes that the most suspected foods in the outbreak are pepperoni pizza and meatball spaghetti. What is the overall attack rate for those who ate meatball spaghetti?

23% To calculate the food-specific attack rate, we need to define how many people are exposed to the specific food and how many people develop the symptoms in the case definition. In this question, we are asking about "overall" attack rate in those people who ate meatball spaghetti, so we have to add "meatball spaghetti only" and "both pepperoni pizza and meatball spaghetti" to get the overall rate. Which is 525 (375 plus 150), who are at risk of exposure, and 119 (62 plus 57), who developed the symptoms, corresponding to 23% of attack rate.

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?

26.7% 56.9 million if the total number of deaths = 100% deaths. There were 15.2 million deaths due to ischemic heart disease or stroke; therefore 15.2 million represents 26.7% of all deaths. Another way to express this number is 26.7% of all deaths were due to ischemic heart disease or stroke: (15.2 × 100)/56.9 = 26.7%.

An epidemiologist decides to investigate the incidence of diabetes in a population of 300 older adults who live in a nursing home. She visits the nursing home in January 1, 2017 and later in December 31 of the same year. She looks into the records of these patients and learns that in her first visit, 25 patients had diabetes and 35 in her second visit. What number should be included in the denominator for her calculation of incidence?

275 Because 25 patients already had diabetes at the beginning of her study, only 275 were at risk of diabetes.

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?

28% 3,956 deaths represent 28% of the total number of cases of Ebola. This proportion is known as the case-fatality rate.

In a cohort study of smoking and myocardial infarction in City A, the number of myocardial infarctions were 250 cases among 7,000 smokers and the number of myocardial infarctions were 150 cases among 20,000 nonsmokers. What is the attributable risk (risk difference) of smoking?

28.2 per 1,000 In this study, the incidence of myocardial infarction among smokers is 35.7 per 1,000 and the incidence among the nonexposed is 7.5 per 1,000. Subtracting the latter from the former, the difference in the incidence rate is 28.2 per 1,000.

Consider the following 2 × 2 table from a hypothetical cohort study. Calculate the relative risk of CVD comparing those with high fasting glucose (≥126 mg/dL) with those with normal fasting glucose (<126 mg/dL)

3.08 In a 2 × 2 table that is set up in this format, we can apply the formula: (a/(a + b))/(c/(c + d)) to calculate the relative risk: (125/(125 + 325))/(50/(50 + 500)) = 3.08.

Epidemiologists decided to investigate the validity of new diagnostic tool for breast cancer. They used this new diagnostic tool for breast cancer in 150 women with biopsy-proven breast cancer in 300 age- and race-matched control women. The results of the new tool were positive in 136 cases and in 35 control women, all of whom showed no evidence of cancer at biopsy. Now, the epidemiologists want to use the new diagnostic tool for screening program in Cities A and B. Based on previous cross-sectional studies, the prevalence of breast cancer is 5% in City A and 1% in City B. What is the expected positive predictive value of new diagnosis tool for breast cancer in City A?

30% The number of people who test positive from people who have cancer equals 4,550 (5,000 multiplied by 0.91; the sensitivity). The number of people who test positive from people who do not have cancer equals 10,450 (95,000 multiplied by 0.11; 1 minus the specificity). The number of people who test positive by the new diagnostic test is 15,000. Therefore the positive predictive value is 0.30 (equals 4,550 divided by 15,000).

In a cohort study of smoking and myocardial infarction in City A, the number of myocardial infarctions were 250 cases among 7,000 smokers and the number of myocardial infarctions were 150 cases among 20,000 nonsmokers. What is the relative risk of smoking in this cohort study?

4.8 The relative risk of myocardial infarction is 35.7 per 1,000 divided by 7.5 per 1,000, which equals 4.8.

The incidence of disease X is 56/1,000 per year among smokers and 33/1,000 per year among nonsmokers. What proportion of cases of disease X are due to smoking among those who smoke?

41% The attributable risk is calculated as follows: (incidence in exposed - incidence in unexposed)/(incidence in exposed); in this example: (56/1,000 - 33/1,000)/(56/1,000) = 0.41, or 41%.

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?

43 Deaths/1000 People The expected number for age greater than 65 equals the "age-specific mortality rate for age older than 65" multiplied by the "age-specific standard population for age older than 65," which is 675 (225 divided by 3,000 multiplied by 9,000). Therefore the age-adjusted mortality rate of City B is 43 deaths per 1,000 people (765 divided by 18,000)

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 positive predictive value of the standard test in City A?

47% Among 1,700 people who identified as test positive, there are 800 people who actually have the disease. Therefore positive predictive value equals 800 divided by 1,700 (equals 0.47).

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?

47% Sensitivity equals the "number of people who identified as diseased by the test" divided by the "number of people who actually have the disease." The sensitivity is 0.47 (136 divided by 290).

What is the mortality from influenza during the 2016 season in the old age group at Minas Tirith?

50 Deaths/1000 People Mortality rate equals the number of deaths divided by the number of people at risk. There are 500 deaths in the young age group, and its population is 10,000 people. The mortality rate is 50 deaths/1,000 people.

What is the crude death rate from disease X for City A?

53 Deaths/1000 People Mortality rate equals number of deaths divided by number of people at risk. There are 480 deaths in City A, and its population is 9,000 people. The mortality rate is 53.3 deaths/1,000 people.

In a cohort study of smoking and myocardial infarction in City A, the number of myocardial infarctions were 250 cases among 7,000 smokers and the number of myocardial infarctions were 150 cases among 20,000 nonsmokers. From another source, a cross-sectional study, we know that 30% of the total population in City A were smokers. What is the population proportion attributable risk of smoking in City A?

53% Using the total population incidence in the PPAR calculation then gives an estimate of 53%. This is found by subtracting 7.5 from 16.0 and dividing this result by 16.0.

The population of Oriol City in June 2018 was 612,437. According to the Oriol City's health department, there were 329 new cases of Raven's disease during 2018. Counting those new cases, by December 31 it was estimated that there were 6580 persons with Raven's disease in Oriol City. What was the incidence rate of Raven's disease in 2018?

54 per 100,000 population

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?

68% Specificity equals the "number of people who were identified as nondiseased by the test" divided by the "number of people who actually do not have the disease." The specificity is 0.68 (351 divided by 516).

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. Using this table, calculate the sensitivity of the test.

70% The test's sensitivity is calculated by dividing the number of true positives (84 in this case) by the total number of people with the disease (120 in this case); 84/120 = 0.70, or 70%.

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?

72% Net sensitivity from sequential tests equals the sensitivity of test 1 multiplied by the sensitivity of test 2. The net sensitivity is 0.72 (0.8 multiplied by 0.9).

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?

84% The simple percent agreement equals the "number of agreements" divided by the "total readings." The simple percent agreement equals 0.84 (210 divided by 250).

Consider the following 2 × 2 table from a hypothetical cohort study. Calculate the incidence of cardiovascular disease (CVD) among the not exposed participants.

9 Per 100 Population In a 2 × 2 table that is setup in this format, we can apply the formula: c/(c + d) to calculate the incidence of disease in the not exposed group: 50/(50 + 500) = 0.09 × 100 = 9% or 9 per 100 population.

Epidemiologists decided to investigate the validity of new diagnostic tool for breast cancer. They used this new diagnostic tool for breast cancer in 150 women with biopsy-proven breast cancer in 300 age- and race-matched control women. The results of the new tool were positive in 136 cases and in 35 control women, all of whom showed no evidence of cancer at biopsy. What is the sensitivity of new diagnosis tool for breast cancer?

91% The sensitivity of the new diagnostic test is the number of positive cases among cases divided by the number of total cases, which equals 136 divided by 150. .

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. What proportion of the patients who tested negative are truly disease free?

96% The negative predictive value is calculated by dividing the number of true negatives (836 in this case) by the total number of negative tests (872 in this case); 836/872 = 0.958, or 96%.

Human papillomavirus (HPV) infections are known to be a cause of cervical cancer. In most cases, HPV goes away on its own and does not cause any health problems. However, the worldwide HPV prevalence in cervical carcinomas is 99.7%. This indicates that HPV-negative carcinoma is extremely uncommon. In this case, HPV is which of the following?

A necessary but not sufficient cause

In the student's health clinic of a certain university, 140 cases of foot-hand-mouth disease were identified among the undergraduate students. This viral infection is usually mild, and none of the students got any complication. Because it is rare to observe this condition in people older than 10 years, the university reported their findings to the city's health department. Three officers were sent to the university to interview and examine all the infected students and their contacts. By sending the three officers, what type of surveillance was implemented by the city health department in response to the university's report?

Active

During the conquest of Mexico, outbreaks played an important role that favored the Spaniards. There were several outbreaks of smallpox that killed thousands of natives. Smallpox was introduced into America by the Europeans. Why were the natives particularly afflicted by smallpox outbreaks?

Among natives, the proportion of susceptible was higher.

What is the best measure of association to explain what percentage of the new diagnoses of disease X are explained by exposure to Y among those exposed to Y?

Attributable risk

The government of Country A decided to introduce a new treatment strategy for disease X. It was decided that, starting in January 1, 2019, all patients diagnosed with disease X in public hospitals would receive the new treatment. Researchers were asked to evaluate the new treatment. Which of the following designs is the best approach to evaluate the new treatment?

Before-after study

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?

Cannot calculate it based on given information

An outbreak of measles occurred in City A. There were 1,000 confirmed cases among children younger than 10 years old. Unfortunately, 50 children died of measles. Fifty represent 5% of the total number of cases. What concept is being illustrated in this example?

Case-fatality rate

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?

City Alpha will have a much higher age-adjusted mortality rate than Beta.

Temporal relationship is a necessary criterion to establish causality. Which of the following epidemiologic study design allows to evaluate temporal relationship?

Cohort

Cardiorespiratory fitness, measured as VO2 max in mL/kg/min (maximum oxygen consumption), is associated with increased longevity. Recent evidence suggests that higher fitness increases the life span. Those with a low VO2 max have a life expectancy after 60 years of 7 years, those with moderate VO2 max of 15 years, and those with a high VO2 max have a life expectancy after 60 of 23 years. Which of the causal criteria is illustrated with this example?

Dose-response effect Increasing fitness is associated with increased life expectancy after age of 60.

What is the name of the occurrence of a clearly higher than expected number of cases of a disease within a limited geographical region?

Epidemic

Which term most accurately describes the following definition? "The occurrence in a community or region of cases of an illness, specific health-related behavior, or other health-related events clearly in excess of normal expectancy." [Porta M, ed. A Dictionary of Epidemiology. New York: Oxford University Press; 2014.]

Epidemic

This historic character observed that childbed fever mortality was more common among women treated by physicians and medical students compared with women treated by midwives. Based on his observations, he implemented a hand wash policy that resulted in a decrease in mortality. Name the character that we are talking about.

Ignaz Semmelweis

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?

Explain that no age adjustment is needed when comparing with age-specific mortality rates.

Which of the following statements is the most accurate interpretation of disease occurrence in City A and City B?

For direct age-adjustment, the weight for a given age category is the number of individuals in the standard population for that age group.

Which of the following statements is not an accurate description of epidemiologic studies using large group data such as National Hospital Discharge Survey or National Health Interview Survey?

Given the large data sets used, sample size is usually considered a major problem.

Over the past century, a marked decline in the mortality rates of many infectious diseases has been observed. Which of the following is the most likely reason for the observed decline in mortality rates from common infectious diseases?

Improvement in social conditions

Which of the following measures represents the absolute risk of getting a disease?

Incidence

For a disease such as seasonal influenza, which is less fatal and of short duration?

Incidence rates will be much higher than mortality rates.

Suppose that the incidence of all types of cancer remains constant in a given country. However, thanks to new treatments, the survival of cancer patients increases. What do you expect to happen to the prevalence of cancer in that country?

Increase prevalence = incidence × duration

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?

Intrasubject variability

A diagnostic test with a very high sensitivity but very low specificity has the following problem:

It will label a big proportion of healthy people as sick (false-positives).

Which of the following statements is the most accurate example of tertiary prevention?

Joining malaria rehabilitation programs to reduce or eliminate long-term impairments and disabilities from previous infections

The usual time to death after diagnosis of disease X is 2 years. A screening program allows for the early detection of disease X, on average 1 year earlier than the usual diagnosis; however, there is no available treatment even in early stages of disease X. With the screening program it seems like the time to death has increased to 3 years; however, this is only due to the early diagnosis thanks to the screening program. What is the name of the issue previously described?

Lead-time bias

Which of the following statement about positive predictive value is the most accurate? Positive predictive value is a fixed characteristic of the test. It will not change over the person, place, and time. Positive predictive value is the probability that a diseased person (case) in the population tested will be identified as diseased by the test. None of above. Specificity will not affect the positive predictive value. Positive predictive value is affected by the sensitivity of the test only.

None of the Above

Which of the following statements is not evidence suggesting Exposure A as a causative agent on Disease X? Exposure A is clearly linked to mediator M. Approximately 11% of mediator M patients will go on to have Disease X over a 10-year period. Many of the observations regarding Exposure A and Disease X have been replicated repeatedly. Eradication of Exposure A heals Disease X at the same rate as other treatment of choice. Prevalence of Exposure A in patients with Disease X is 90% to 100%. None of above

None of the above

The following is a measure of the strength of association, typically used in case-control studies to measure the association between exposure and disease:

Odds Ratio Odds ratio is a measure of the strength of an association that is typically used in case-control studies.

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 results of the test. To answer that question, Dr. Gordis must know what about the test?

Positive predictive value

There was a food poisoning outbreak on April 1, 2022, at the City Z Food Safety Conference. There were 1,000 people registered for the conference with luncheon, 100 volunteers to host attendees, and 50 people who served the luncheon during the conference. Except for 50 people who served the food, all of the participants and volunteers ate the food from the luncheon at the conference on April 1, 2018. After an initial outbreak of food poisoning is reported, an epidemiologist sends surveys to all people at risk to investigate the cause. However, only 900 people among those at risk answer the survey. After analysis of 900 survey results, the epidemiologist concludes that the most suspected foods in the outbreak are pepperoni pizza and meatball spaghetti. What is the most suspected food for food poisoning after cross-tabulation? Use the following table to answer the question. Summary of Survey Responses

Pepperoni Only Pepperoni pizza only attack rate is 41.09% (113 divided by 275), and meatball spaghetti only is 16.53% (62 divided by 375). The attack rate of both pepperoni pizza and meatball spaghetti is 38.00% (57 divided by 150). Some may choose both of them which are the most suspected food. If both the foods were the most suspected food, we should have a higher attack rate in meatball spaghetti only group as well.

According to the healthy people 2020, the following is an indicator of access to health services:

Persons with a usual primary care provider

A politician asks an epidemiologist how many cases of coronary heart disease can be prevented if they manage to eliminate the exposure to smoking in city A. The epidemiologists explain that, if they eliminate smoking, they could prevent 22% cases of coronary heart disease. What measure of association was used to answer this question?

Population attributable risk

Epidemiologists decided to investigate the validity of new diagnostic tool for breast cancer. They used this new diagnostic tool for breast cancer in 150 women with biopsy-proven breast cancer in 300 age- and race-matched control women. The results of the new tool were positive in 136 cases and in 35 control women, all of whom showed no evidence of cancer at biopsy. Now, the epidemiologists want to use the new diagnostic tool for screening program in Cities A and B. Based on previous cross-sectional studies, the prevalence of breast cancer is 5% in City A and 1% in City B. What is the most reasonable conclusion to be drawn from these data?

Positive predictive value of new diagnostic tool for breast cancer in City A is higher than expected positive predictive value in City B.

In the model of the Natural History of Disease, when is the ideal time to do screening for a disease?

Preclinical phase

Which of the following statements is the most accurate example of primary prevention?

Promoting antismoking campaign in the community

A recent study found that screening for disease X led to increased survival. In the study, those who were screened were generally younger, healthier, and more aware of their health than those who were not screened. This makes it hard to evaluate whether the improvement in survivorship was due to the screening program or due to the characteristics of those who are screened. What is the name of this issue when evaluating the effect of a screening program?

Selection bias

Which of the following statements is the most accurate definition?

Sentinel surveillance is a type of surveillance based on selected population samples chosen to represent the relevant experience of particular groups.

Thanks to the contributions of Edward Jenner, the following disease was eradicated later by efforts organized by D.A. Henderson:

Smallpox

Which of the following is an example of tertiary prevention?

Surgical amputation of an extremity with osteosarcoma (bone cancer)

Which of the following statements is the most accurate example of secondary prevention?

Taking a routine Pap smear test

In a hypothetical cross-sectional study, marriage was found to be strongly associated with increased levels of happiness. The authors concluded that marriage was a cause of happiness. However, a reviewer of this study argued that because it is a cross-sectional study, it could not be determined whether marriage caused happiness or happiness caused marriage. What criterion of causal relationships was not met in the study according to the reviewer? Temporal relationship Dose-response Replication of findings Biologic plausibility Strength of association

Temporal relationship

Which of the following statements is the most accurate definition of efficacy?

Testing a drug in a group of participants who have agreed to join clinical trial.

Which of the following statements is the most accurate definition of effectiveness?

Testing a vaccine in a community where some of individuals do not want to be vaccinated.

Which of the following statements is the most accurate description of the attributable risk (deaths per 100,000) of coronary heart disease for smokers in this study?

The attributable risk of coronary heart disease deaths is 400 deaths per 100,000. The risk of coronary heart disease deaths among smokers is 700 per 100,000, and the risk of coronary heart disease deaths among nonsmokers is 300 per 100,000. The attributable risk is 400 per 100,000.

The following is a reason for an apparent lack of benefit from a screening program:

The available treatments are not effective even when administered early in the disease progression.

Which of the following statements is the most accurate definition of efficiency?

The effects or end results achieved in relation to the effort expended in terms of money, resources, and time.

What is the most accurate definition of the incubation period (of an infectious disease)?

The interval from receipt of infection to the time of onset of clinical illness (the onset of recognizable symptoms)

A researcher finds that the standardized mortality rate (SMR) for epidemiologists compared with the general population is 100. What does that mean?

The observed number of deaths for epidemiologists is the same as the expected.

The following are problems generated when a patient is given a false-positive diagnosis, except:

The opportunity for an effective intervention is missed.

Which of the following statements about specificity is the most accurate?

The probability that a person without the disease (noncase) in the population tested will be identified as nondiseased by the test.

Which of the following statements is the most accurate description of the risk and relative risk of lung cancer deaths in this study?

The risk of lung cancer death is 2.1 times greater in smokers compared with nonsmokers. The risk of lung cancer deaths among smokers is 150 per 100,000, and the risk of lung cancer deaths among nonsmokers is 70 per 100,000. The relative risk of lung cancer deaths by smoking is 150 divided by 70, which equals 2.1.

In the model of the Natural History of Disease, the period of time between the onset of signs and symptoms of disease and its ultimate outcome (cure, control, or death) is known as

clinical phase

When testing whether we can achieve a less expensive and better way to treat a disease with an intervention that has shown to work previously, we are looking for

efficiency

Lack of physical activity is a known factor associated with colon cancer. However, colon cancer develops even among active individuals. Moreover, several individuals who perform very little levels of physical activity never develop colon cancer. Hence, in the causal relationship between physical inactivity and colon cancer, the lack of physical activity is

neither necessary not sufficient.

In general terms, a health indicator is a

sentinel condition that is assumed to reflect the general level of health care.