Epidemiology quiz

1.

Question 1 is based on the following information: Reliability lectures

Two oncologists, Drs. Nodule and Smith independently examined 200 biopsies for evidence of invasive breast cancer.

· Dr. Nodule diagnosed 20 biopsies as “positive” for invasive breast cancer.

· Dr. Smith diagnosed 15 biopsies as “positive” for invasive breast cancer, 10 of which were also diagnosed as positive by Dr. Nodule.

Calculate the % positive agreement between Drs. Nodule and Smith. Please round to the nearest percent.

a. 93%

b. 50%

c. 43%

d. 40%

e. 34%

A:

Yes 20 , No 180

B:

Yes 10 , No 190

20+190/200

1 point

2.

In a study using electronic health records, 40 patients diagnosed as having dengue fever were recruited along with 40 patients with non-dengue febrile illness who were matched for age, sex, and race to the dengue patients. To determine if fasting is associated with clinical dengue, hospital charts were then reviewed to determine whether these patients also fasted prior to their illness. What epidemiologic study design is described here? (Select one) Study design lecture

a. cross-sectional study

b. case-control study

c. prospective cohort study

d. retrospective cohort study

e. clinical trial

1 point

3.

In screening, if people who are screened appear to have better survival outcomes only because the disease was identified earlier, but not because death was delayed, this is what type of bias? (Select one) Bias lectures

a. Recall bias

b. Reporting bias

c. Bias due to length-based sampling

d. Lead time bias

1 point

4.

Which of the following is an example of an observational cohort study that might be used to assess the association between agent X and disease Y? (Select one)

a. A group of individuals exposed to agent X are recruited in 1995 and followed until 2004 at which time they are tested for the presence of disease Y.

b. A group of individuals with disease Y and without disease Y are recruited and interviewed about exposure to agent X in 2004.

c. A group of individuals exposed to agent X and a group of individuals not exposed to agent X are recruited and tested for disease Y in 1995.

d. A group of individuals with disease Y and without disease Y are recruited in 2004 and their past health records screened for documentation of exposure to agent X in 1995

e. A group of individuals without disease Y are recruited in 2004 and their past health records screened for documentation of exposure to agent X in 1995

1 point

5.

Question 5 is based on the following abstract:

Objectives. This study aimed to clarify the relationship between community water fluoridation (CWF) and intelligence (IQ) in New Zealand.

Methods. We conducted a study of a general population sample of those born in Dunedin, New Zealand, between April 1, 1972, and March 30, 1973 (95.4% retention after 38 years of follow- up). Residence in a CWF area, use of fluoride dentifrice and intake of 0.5-milligram fluoride tablets were assessed in early life (prior to age 5 years); we assessed IQ repeatedly between ages 7 to 13 years and at age 38 years.

Results. No clear differences in IQ because of fluoride exposure were noted. These findings held after adjusting for potential confounding variables, including sex, socioeconomic status, breastfeeding, and birth weight (as well as educational attainment for adult IQ outcomes).

Conclusions. These findings do not support the assertion that fluoride in the context of CWF programs is neurotoxic. Associations between very high fluoride exposure and low IQ reported in previous studies may have been affected by confounding, particularly by urban or rural status.

Which epidemiologic study design is described above? (Select one) Study Design lectures

a. Prospective cohort study

b. Case-control study

c. Cross-sectional study

d. Clinical trial

e. Ecological study

1 point

6.

Questions 6 and 7 are based on the following:

The table below gives information on Town A and Town B in 2012. Assume that the population is precise (i.e., there is no need to estimate mid-year population) and all deaths are precisely identified for the year.

What is the crude mortality rate in Town A in 2012? (Select one) Populations lectures

a. 8.9 per 100 person-months

b. 12.1 per 100 person-months

c. 8.9 per 100 persons

d. 12.1 per 100 persons

e. 2.7 per 100 persons

1 point

7.

Using the direct adjustment method and combined populations of Town A and B as the standard population, what is the age-adjusted mortality rate in Town A?

a. 10.9 per 100 person-months

b. 15.4 per 100 person-months

c. 22.6 per 100 person-months

d. 10.9 per 100 persons

e. 15.4 per 100 persons

1 point

8.

Use the following information for questions 8 and 9:

Two tests (A and B) for osteoporosis have the following characteristics:

· Test A has a sensitivity of 60% and a specificity of 80%.

· Test B has a sensitivity of 90% and a specificity of 90%.

A nurse first uses Test A. Patients who test positive on Test A are then given Test B. Testing positive on both tests is diagnostic of osteoporosis. What is the net sensitivity of this testing approach?

a. 54%

b. 65%

c. 82%

d. 90%

e. 98%

1 point

9.

If the nurse reversed the order of the testing (i.e. used Test B first and the administered Test A to those who were positive on Test B), what would happen to the net specificity?

a. decrease

b. stay the same

c. increase

d. not enough information to tell

1 point

10.

You are conducting your own study and decide to review some of the measurement logs with your research assistant. You discover that the research assistant used the wrong threshold to classify participants as having pre-clinical disease. This is an example of:

a. Selection bias

b. Modification bias

c. Confounding bias

d. Information bias

1 point

11.

Question 11 and 12 are based on the following information:

The incidence of heart attacks among smokers in a community is 30.0 per 100,000 per year. The incidence of heart attacks among non-smokers in this community is 4.0 per 100,000 per year. The proportion of non-smokers in this community is 75%.

What proportion of the risk of heart attacks among smokers can be attributed to smoking? (Select one)

a. 6.5%

b. 26.0%

c. 76.0%

d. 86.7%

1 point

12.

What proportion of the risk of heart attacks in the total population can be attributed to smoking? (Select one)

a. 21.3%

b. 61.9%

c. 82.2%

d. Cannot be calculated given the information provided.

1 point

13.

In examining the association between an exposure and outcome, which of the following is true about a confounding variable? (Select ALL)

a. A confounder is a result of the exposure.

b. A confounder is not a risk factor of the outcome of interest.

c. A confounder alters the observed association between the exposure and outcome.

d. A confounder is associated with the exposure of interest.

1 point

14.

To develop Disease Z, an individual must have been exposed to environmental toxin A. Some individuals exposed to environmental toxin A, though, will not develop Disease Z.

Based on the above information, environmental toxin A is ________ for developing Disease Z:

a. Necessary and sufficient

b. Necessary but not sufficient

c. Not necessary and not sufficient

d. Not necessary but sufficient

1 point

15.

Which of the following is true for simultaneous testing? (Select one)

a. Net specificity is greater than the specificity of either test alone

b. Net specificity is less than the specificity of either test alone

c. Net specificity is the same as that of the more specific test

d. Net specificity is the same as that of the less specific test

1 point

16.

Question 16 is based on the following adapted abstract:

Maternal vitamin D deficiency has been suggested to influence fetal and neonatal health. Little is known about vitamin D status in Chinese pregnant women. The purpose of this study was to assess the vitamin D status of pregnant women residing in Beijing in winter and evaluate the impact of maternal factors on serum 25-hydroxyvitamin D [25(OH)D] levels. The study was conducted on 125 healthy pregnant women. For each individual, data concerning pre-pregnancy weight, educational status, use of multivitamins and behavioral factors such as daily duration of computer use, walking and sun exposure were obtained. Serum concentrations of 25(OH)D were measured by enzyme-linked immunosorbent assay. The prevalence of vitamin D deficiency (25(OH)D < 50 nmol/L) was 96.8% and almost half (44.8%) of women were severely vitamin D deficiency (25(OH)D < 25 nmol/L). The concentration of 25(OH)D was lower in women with shorter duration of sun exposure (≤ 0.5 h/day, 25.3 ± 8.9 nmol/L) than that in women with longer duration of sun exposure (> 0.5 h/day; 30.3± 9.5 nmol/L; P = 0.003). Thirty-six women (28.8%) had sun exposure duration ≥ 1.5h/day. The 25(OH)D concentration in these women was 31.5 ± 9.4 nmol/L which was also much lower than the normal level. Women who reported taking a multivitamin supplement had significantly higher 25(OH)D concentrations (32.3 ± 9.5 nmol/L) when compared with non-users (24.9 ± 8.2 nmol/L; P < 0.001). Pregnant women in Beijing are at very high risk of vitamin D deficiency in winter. Duration of sun exposure and the use of multivitamin were the most important determinants for vitamin D status. 

Which type of epidemiologic study design is described in the above abstract? (Select one)

a. Clinical trial

b. Ecologic study

c. Cross-sectional study

d. Cohort study

1 point

17.

Question 17 is based on the article described at the following webpage:

https://www.statnews.com/2017/01/26/herpes-testing-false-positives/

Excerpt: “Blood tests [for herpes] can be highly unreliable. The kind of test used to diagnose Lauren, an IgM test, has long been rejected by the Centers for Disease Control and Prevention but is still used by some clinicians. Meanwhile, the CDC and the US Preventive Services Task Force concur that the most widely available herpes test, called HerpeSelect, should not be used to screen asymptomatic people because of its high risk of false positives: Up to 1 in 2 positive tests could be false, according to the USPSTF’s most recent guidelines.”

Based solely on the article, what is the problem with current testing for herpes using the most widely available test “HerpeSelect”? (Select one)

a. Low sensitivity

b. Low reliability

c. Low negative predictive value

d. Low specificity

1 point

18.

A study was undertaken to investigate the effect of asbestos exposure on lung cancer among employees at Factory A. In 2016, a group of 35,091 employees who worked at the factory from 1968 to 1994 and had cancer follow-up data available through 2015 were included in the study. Asbestos exposure was defined categorically based on whether the employee worked on site (exposed) or in the management building nearby (unexposed). The incidence rate among those who worked on site was then compared to the incidence rate among those who did not. Which type of epidemiologic study design is described above?

a. Cross-sectional study

b. Case-control study

c. Prospective cohort study

d. Retrospective cohort study

e. Clinical trial

1 point

19.

Internal validity of an epidemiologic study refers to the extent that… (Select one)

a. The study was conducted with robust methods and findings are not likely due to error, bias, and/or confounding

b. The findings of the study are able to be confirmed by other investigators using the same methods

c. The participants in the study are representative of all individuals with the specific outcome of interest

d. The human subjects completed the informed consent process before data collection commenced

1 point

20.

Question 20 and 21 are based on the following table:

Number of students by amount of Twitter use (exposure) and satisfaction with life (outcome) in a cross-sectional study of 300 JHU undergraduates

Calculate the prevalence ratio for the association between moderate amount of Twitter use (compared to low amount) and more satisfaction with life. (Select one)

a. 0.18

b. 0.30

c. 0.61

d. 0.78

1 point

21.

Based on the table, the conclusion that Twitter use causes less satisfaction with life is: (Select one)

a. Justified because the risk for being more satisfied with life is less than 1 for both high and moderate amount of Twitter use compared to low amount of Twitter use

b. Justified because the study was conducted among JHU undergraduates who are representative of all undergraduate Twitter users

c. Not justified because a cross-sectional study cannot establish temporality, something that is necessary in order to establish causality

d. Not justified because the relative risks were weak, thus failing the causal guideline of strength of association, something that is necessary in order to establish causality

1 point

22.

Question 22 is based on the following information:

An experimental study was conducted to assess the effect of receiving Drug A alone compared to placebo (no treatment) in people with rheumatoid arthritis (RA) for preventing the worsening of RA symptoms. All participants were observed for the same length of time. The findings of the study are summarized in the below table.

Based on the above data, what is the estimate of the relative risk for association for the relationship between Drug A (vs. placebo) and worsening of RA symptoms? (Select one)

a. 0.29

b. 0.35

c. 1.20

d. 3.44

1 point

23.

Questions 23-25 are based on the following information:

Providers at a university student health center in Baltimore noticed an increased number of patients with acute gastroenteritis and fever over a six-day period in December 2014. Investigators from the Baltimore City Health Department were notified, and an epidemiologic investigation was undertaken to determine the cause of the outbreak. Blood and stool samples were collected.

Laboratory data indicated that the organism causing the gastroenteritis was Salmonella. Two hundred students (80 sick and 120 not sick) were interviewed, and many reported having eaten at The Rusty LunchBucket, a soup-salad-and-sandwich deli on campus. Each person was asked whether they had eaten soup, salad, or sandwich, or any combination of the three. Data from the investigation are provided below.

What is the cumulative incidence of sickness among individuals who reported eating salad?

a. 65%

b. 39%

c. 41%

d. 29%

1 point

24.

Which food was most likely contaminated with Salmonella? (Select one)

a. Soup

b. Salad

c. Breadsticks

d. Sandwich

1 point

25.

Question 25 is based on the following additional information:

Patients reported onset of illness during each of the following days:

“Number sick by end of the day” refers to the number of individuals who became sick within the day indicated by the “Days since exposure”.