1. Diabetes prevalence probability curves.
 Diabetes prevalence probability curves. The horizontal axis reflects the probability of diabetes among positive screenees; the vertical axis indicates the prevalence of diabetes per thousand population at risk. The different curves correspond to different cut points of the blood glucose test, varying from 70 mg to 160 mg per 100 ml of venous blood two hours after a meal. The sensitivity and the specificity of the tests are 64.3% and 96.9% respectively. This graph shows that the probability of diabetes among positive screenees (positive predictive value) increases as the prevalence of diabetes increases, and the probability also goes up when the cut point is set higher assuming the same prevalence and a constant sensitivity and specificity; to convert mg/100 ml to mmol/l multiply by (source: Kessel23).
A Morabia, and F F Zhang Postgrad Med J 2004;80:
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