Epidemiology Flashcards
How do you interpret the following 95% confidence interval (CI) for a relative risk (RR) of 0.582: 95% CI 0.502, 0.673?
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)
Bias introduced into a study when a clinician is aware of the pt’s tx type
Observational bias
Bias introduced when screening detects a dz earlier and thus lengthens the time from diagnosis to death
Lead-time bias
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 _________.
Confounding variable
The proportion of ppl who have the dz and test (+) is the ______.
Sensitivity
Sensitive tests have few false (-)s are are used to rule ___ a dz.
Out
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?
Highly sensitive for TB. Screening tests with high sensitivity are good for diseases w/ low prevalence
Chronic diseases such as SLE - higher prevalence or incidence?
Higher prevalence
Epidemics such as influenza - higher prevalence or incidence?
Higher incidence
What is the difference between incidence and prevalence?
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.
Cross-sectional survey - incidence or prevalence?
Prevalence
Cohort study - incidence or prevalence?
Incidence and Prevalence
Case-control study - incidence or prevalence?
Neither
Describe a test that consistently gives identical results, but the results are wrong.
High reliability (precision), low validity (accuracy)
Difference between a cohort and a case-control study
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
Attributable risk?
The difference in risk in the exposed and unexposed groups (ie, the risk that is attributable to the exposure).
Relative risk?
Incidence in the exposed group divided by the incidence in the nonexposed group.
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?
In pts who took ASA, the risk of heart dz was 1.5 times that of pts who did not take ASA.
Odds ratio
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.
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?
In patients who took ASA, the odds of acquiring heart dz were 1.5 times those of pts who did not take ASA
In which pts do you initiate colorectal cancer screening early?
Patients with IBD; those with familial adenomatous polyposis (FAP)/hereditary nonpolyposis colorectal cancer (HNPCC); and those who have first-degree relatives with adenomatous polyps (
The most common cancer in men and the most common cause of death from cancer in men
Prostate cancer is the most common cancer in men, but lung cancer causes more deaths.
The percentage of cases within 1 SD of the mean? Two SDs? Three SDs?
68%, 95.4%, 99.7%
Birth rate?
Number of live births per 1000 population in 1 year
Mortality rate?
Number of deaths per 1000 population in 1 year
Neonatal mortality rate?
Number of deaths from birth to 28 days per 1000 live births in 1 year
Infant mortality rate?
Number of deaths from birth to 1 year of age per 1000 live births (neonatal + postnatal mortality) in 1 year
Maternal mortality rate?
Number of deaths during pregnancy to 90 days postpartum per 100,000 live births in 1 year
