Rapid Review: Epidemiology

Question 1

How do you interpret the following 95% confidence interval for a relative risk of .582: .502, .673

Answer 1

These data are consistent with relative risks range from .502 to .673 with 95% confidence (the true RR will be between .502 and .673 95/100 times)

Question 2

Bias introduced into a study when a clincian is aware of the patient’s treatment type

Answer 2

Observational bias

Question 3

Bias introduced when screening detects a disease 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 people who have the disease and test + is the ___

Answer 5

Sensitivity=TP/(TP+FN)

Question 6

Sensitive tests have few ___ and are used to rule ___ a disease

Answer 6

Negatives, out

Question 7

PPD reactivity is used as a screening test because most people with TB will have a + PPD. Highly sensitive or specific?

Answer 7

Sensitive

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 (but not really)

Question 10

What is the difference between incidence and prevalence?

Answer 10

Prevalence is the percentage of cases of disease in a population at 1 snapshot in time. Incidence is the percentage of new cases of disease 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

Both

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 case-control study

Answer 15

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

Cohort studies compares those with a risk factor to those who do not have the risk factor. Case control studies compare people with a target disease to those who don’t have the target disease.

Question 16

Attributable Risk?

Answer 16

The difference in risk in the exposed and unexposed groups

Question 17

Relative Risk

Answer 17

Incidence in the exposed group divided by the incidence in the unexposed group

Question 18

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

Answer 18

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

Question 19

Odds ratio?

Answer 19

In cohort studies, the odds of developing the disease in the exposed group divided by the odds of developing the disease in the nonexposed 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 disease divided by the odds that the nonexposed group has the disease

Question 20

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

Answer 20

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

Question 21

In which patients do you initiate colorectal cancer screening early?

Answer 21

Patients with IBD, FAP, HNPCC, first degree relatives with adenmatous polyps or colorectal cancer

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? 2 SDs? 3 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 in 1 year

Question 28

Maternal mortality rate?

Answer 28

Number of deaths during pregnancy to 90 days pospartum per 1000,000 live births in 1 year