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?
The data are consistent with RRs ranging from 0.502 to 0.673 with 95% confidence (I.e we are confident that 95 out of 100 times the true RR will be between 0.502 and 0.673)
Bias introduced into a study when a clinician is aware of the patient’s treatment type
Observational bias
Bias introduced when screening detects a disease earlier and thus lengthens the time from diagnosis to death, but does not improve survival
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 who have the disease and test + is the ………
Sensitivity
Sensitive tests have few false - 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 have a + 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 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 disease in a population at one point in time
Incidence is the percentage of new cases of disease that develop over a given time period among the total population at risk
Prevalence = incidence x duration
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 divides groups by an exposure and looks for development of disease
Case-control divides groups by a disease and assigns 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 non-exposed group
The results of a hypothetical study found an association between aspirin intake and risk of heart disease. How do you interpret an RR of 1.5?
In patients who took aspirin, the risk of heart disease was 1.5 times that of patients who did not take aspirin
Odds ratio?
Cohort studies: odds of developing the disease in the exposed group divided by the odds of developing the disease in the non exposed group
Case-control: odds that the cases were exposed divided by the odds that the controls were exposed
X-sectional: odds that the exposed group has the disease divided by the odds that the non-exposed group has the disease
Most common cancer in men and most common cause of death from cancer in men
Prostate cancer is most common in men; but lung cancer causes more deaths
Percentage of cases within 1 standard deviation (SD) of the mean?
2SDs?
3SDs?
68%
- 4%
- 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 rates?
Number of deaths from birth to 28days per 1000 live births in 1 year
Infant mortality rates?
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
