Epidemiology

Question 1

How do you interpret the following 95% confidence interval (CI) for a relative risk (RR) of 0.582: 95% CI 0.502, 0.673?

Answer 1

These data are consistent w/ RRs ranging from 0.502 to 0.673 with 95% confidence (ie, we are confident that the true RR will be between 0.502 and 0.673 95 out of 100 times)

Question 2

Bias introduced into a study when a clinician is aware of the pt’s tx type

Answer 2

Observational bias

Question 3

Bias introduced when screening detects a dz earlier and thus lengthens the time from diagnosis to death

Answer 3

Lead-time bias

Question 4

If you want to know if geographical location affects infant mortality rate, but most variation in infant mortality is predicted by socioeconomic status, then socioeconomic status is a _________.

Answer 4

Confounding variable

Question 5

The proportion of ppl who have the dz and test (+) is the ______.

Answer 5

Sensitivity

Question 6

Sensitive tests have few false (-)s are are used to rule ___ a dz.

Answer 6

Out

Question 7

PPD reactivity is used as a screening test because most ppl with TB (except those who are anergic) will have a (+) PPD. Highly sensitive or specific?

Answer 7

Highly sensitive for TB. Screening tests with high sensitivity are good for diseases w/ low prevalence

Question 8

Chronic diseases such as SLE - higher prevalence or incidence?

Answer 8

Higher prevalence

Question 9

Epidemics such as influenza - higher prevalence or incidence?

Answer 9

Higher incidence

Question 10

What is the difference between incidence and prevalence?

Answer 10

Prevalence is the percentage of cases of dz in a population at 1 snapshot in time. Incidence is the percentage of new cases of dz that develop over a given time period among the total population at risk.

Question 11

Cross-sectional survey - incidence or prevalence?

Answer 11

Prevalence

Question 12

Cohort study - incidence or prevalence?

Answer 12

Incidence and Prevalence

Question 13

Case-control study - incidence or prevalence?

Answer 13

Neither

Question 14

Describe a test that consistently gives identical results, but the results are wrong.

Answer 14

High reliability (precision), low validity (accuracy)

Question 15

Difference between a cohort and a case-control study

Answer 15

Cohort studies can be used to calculate RR, incidence, and/or odds ratio (OR). Case-control studies can be used to calculate an OR, which is an estimate of RR when the dz prevalence is low

Question 16

Attributable risk?

Answer 16

The difference in risk in the exposed and unexposed groups (ie, the risk that is attributable to the exposure).

Question 17

Relative risk?

Answer 17

Incidence in the exposed group divided by the incidence in the nonexposed group.

Question 18

The results of a hypothetical study found an association between ASA intake and risk of heart dz. How do you interpret an RR of 1.5?

Answer 18

In pts who took ASA, the risk of heart dz was 1.5 times that of pts who did not take ASA.

Question 19

Odds ratio

Answer 19

In cohort studies, the odds of developing the dz in the exposed group divided by the odds of developing the dz in the non exposed group

In case-control studies, the odds that the cases were exposed divided by the odds that the controls were exposed.

In cross-sectional studies, the odds that the exposed group has the dz divided by the odds that the nonexposed group has the dz.

Question 20

The results of a hypothetical study found an association between ASA intake and risk of heart dz. How do you interpret an OR of 1.5?

Answer 20

In patients who took ASA, the odds of acquiring heart dz were 1.5 times those of pts who did not take ASA

Question 21

In which pts do you initiate colorectal cancer screening early?

Answer 21

Patients with IBD; those with familial adenomatous polyposis (FAP)/hereditary nonpolyposis colorectal cancer (HNPCC); and those who have first-degree relatives with adenomatous polyps (

Question 22

The most common cancer in men and the most common cause of death from cancer in men

Answer 22

Prostate cancer is the most common cancer in men, but lung cancer causes more deaths.

Question 23

The percentage of cases within 1 SD of the mean? Two SDs? Three SDs?

Answer 23

68%, 95.4%, 99.7%

Question 24

Birth rate?

Answer 24

Number of live births per 1000 population in 1 year

Question 25

Mortality rate?

Answer 25

Number of deaths per 1000 population in 1 year

Question 26

Neonatal mortality rate?

Answer 26

Number of deaths from birth to 28 days per 1000 live births in 1 year

Question 27

Infant mortality rate?

Answer 27

Number of deaths from birth to 1 year of age per 1000 live births (neonatal + postnatal mortality) in 1 year

Question 28

Maternal mortality rate?

Answer 28

Number of deaths during pregnancy to 90 days postpartum per 100,000 live births in 1 year