Population Health Flashcards
Main reason for increased life expectancy in Canadians
Decreased infant mortality rate
Lead time bias
Overestimate the survival time from dx b/c screening at occult stage of dz vs dx at later stage
Length time bias
Overestimate the survival time due to screening at one point including more stable cases than aggressive cases, who may have shorter survival times
Screening test must have high sensitivity or specificity?
High sensitivity
Incidence
# new cases in a time interval / persons at risk in time interval Measures rate of new infections
Prevalence
# existing cases at a point in time / persons at risk at that time Measures frequency of disease at a point in time
Top 5 causes of mortality in women in Canada
Cancer Heart disease Stroke Chronic lower respiratory dz Accidents
Top 5 causes of mortality in men in Canda
Cancer Heart disease Accidents Chronic lower respiratory dz Stroke
Specific test
Use to rule IN a hypothesis
Very few false positives
Sensitive test
Use to rule OUT a hypothesis
Very few false negatives
Likelihood Ratio definition
Likelihood that a given test result would be expected in a pt with disease compared with likelihood that same result would be expected in pt without disease
Likelihood ratio + equaiton
Sensitivity / (1- specificity) = (TP / (TP + FN)) / (FP/(TN+FP)
How much the probability of a disease increases if the test is positive
Likelihood ratio - equation
(1-sensitivity)/specificity = (FN/(TP+FN)) / (TN/(TN+FP))
How much the probability of disease decreases if the test is negative
Positive predictive value
Proportion of ppl with +ve test who have the disease
PPV = TP / (TP + FP)
Negative predictive value
Proportion of ppl with -ve test who don’t have the disease
NPV = TN / (TN + FN)
Sensitivity
Proportion of ppl with disease who have a +ve test