Epidemiology Flashcards
Bias introduced into a study when a clinician is aware of the patient’s treatment type
Observation bias
Bias introduced when screening detects a disease earlier and thus lengthens the time from diagnosis to death, but does not improve surgical
Lead-time bias
If you want to know if geographic 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 people with the disease who have a positive test is called what?
Sensitivity
Sensitive tests have few false negatives and are used to rule ____ a disease.
out
PPD reactivity is used as a screening test because most people with TB (except those who are anergic) will has a positive PPD. Highly sensitive or specific?
Highly sensitive for TB. Screening tests with high sensitivity are good for diseases with low prevalence.
Chronic diseases such as systemic lupus erythematosus - 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: percentage of people in a population with a disease at one point in time Incidence: percentage of people in a population that develop a disease over a given time period among the total at-risk population
Cross-sectional survey - reveals incidence or prevalence? Cohort study? Case-control study?
Cross-sectional: Prevalence Cohort: Incidence and prevalence Case-control: 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 case-control study
Cohort: divides groups by exposure and looks for development of disease Case-control: divides group into disease and controls, and then goes back and looks for exposures
Attributable risk
The difference in risk in the exposed and unexposed groups (i.e. the risk that is attributable to the exposure)
Relative risk
Incidence in the exposed group divided by the incidence in the nonexposed group
Meaning of odds ratio in cohort, case-control, and cross-sectional studies
Cohort: odds of developing the disease in the exposed group divided by the odds of developing the disease in the nonexposed group Case-control: odds that the cases were exposed divided by the odds that the controls were exposed Cross-sectional: odds that the exposed group has the disease divided by the odds the nonexposed group has the disease
