Figure 1. Table for calculating the accuracy of a diagnostic test. True Classification Diagnostic Test Disease present (+) Disease absent (-) Disease present(+) a = True positive b = False positive Disease absent(-) c = False negative d = True negative a + c b + d

Figure 2. Method for calculating sensitivity and specificity of a diagnostic test. Term Definition Calculation Sensitivity = % of patients with the disease who test positive = a/(a + c) x 100 Specificity = % of patents who do NOT have disease who test negative = d/(b + d) x 100

% of patients with a positive test who have the disease = Figure 3. Method for calculating positive predictive value (PPV) and negative predictive value (NPV) of a diagnostic test. Term Definition Calculation PPV = % of patients with a positive test who have the disease = a/(a + b) x 100 NPV = % of patents with a negative test who do NOT have the disease = d/(c + d) x 100