Review – Key Chapters Chapter 2 Chapter 3 Chapter 5 Chapter 6

Review – Final Incidence and Prevalence Cumulative incidence Incidence Rate Age standardization Risk difference (attributable risk in exposed) Risk ratio Population attributable risk Attributable proportion In exposed Total population

Review – Final Odds Ratio Confounding Effect Modification Sensitivity – Specificity Positive predictive value Negative predictive value Criteria for causality

Among the Exposed Attributable Risk, rate/risk difference (RD) RD= Re – Ru Excess risk of death associated with the exposure among those exposed the number of cases that would be eliminated if the exposure was eliminated among those exposed Public health impact of the exposure among exposed Attributable Proportion among the exposed, Etiologic Fraction APe=[(Re-Ru)/Re] X 100 The proportion of disease among the exposed that would be eliminated if the exposure were eliminated

Among the Total Population Population Attributable Risk (PAR) or Population rate/risk difference (PRD) PRD= Rt – Ru=RD X Pe Excess risk of death associated with the exposure in the total population the number of cases that would be eliminated if the exposure was eliminated in the total population Public health impact of the exposure in the total population Attributable Proportion in the total population APt=[(Rt-Ru)/Rt] X 100 The proportion of disease in the total population that would be eliminated if the exposure were eliminated

Measures of Association Risk Ratio = [a/(a + b)] / [c/(c + d)] = [prevalence or incidence of outcome for the exposed group] divided by [prevalence or incidence of the outcome for the unexposed group]   Risk Difference = [a/(a + b)] - [c/(c + d)] = [prevalence or incidence of outcome for the exposed group] minus [prevalence or incidence of the outcome for the unexposed group]

Measures of Association Attributable Proportion among Exposed=Etiologic Fraction = (Re-Ru)/Re= [a/(a + b)] - [c/(c + d)] / [a/(a + b)] = Proportion of the prevalence or incidence of the outcome for the exposed group that can be attributed to the exposure.   Population Attributable Proportion = Rt-Ru/Rt=[(a + c) / (a + b + c + d)] - [c/(c + d)] / [(a + c) / (a + b + c + d)] = Proportion of the total prevalence or incidence that can be attributed to the exposure.

Suitable Test Disease Status (Truth) Yes No Total Positive a b a + b   Yes No Total Positive a b a + b Negative c d c + d a + c b + d a + b + c+ d Screening Test Result Sensitivity - enables you to pick up the cases of disease -- a / a + c = those that test positive / all with disease Specificity - enables you to pick out the no diseased people -- d / b + d = those that test negative / all without disease Valid test has high sensitivity and specificity

Suitable Test Disease Status (Truth) Yes No Total Positive a b a + b   Yes No Total Positive a b a + b Negative c d c + d a + c b + d a + b + c+ d Screening Test Result