Aggregating multiple test results to improve medical decision-making
Fig 3
Positive predictive value (PPV) and negative predictive value (NPV) as a function of prevalence f.
The results that we show in panels (A,C) and (B,D) are based on AND and OR aggregations of n = 2 tests, using Eqs (14) and (15), respectively. We denote the sensitivities and specificities of the two tests i ∈ {1, 2} by TNRi and TNRi, respectively. We consider two different combinations of true positive and true negative rates (solid black lines: TNRi = 0.95 and TNRi = 0.95; dashed red lines: TNRi = 0.90 and TNRi = 0.90). As a reference, we also show results for single tests without further aggregation (dash-dotted blue line: TNR = 0.95 and TNR = 0.95; dash-dot-dotted orange line: TNR = 0.90 and TNR = 0.90). These curves are independent of the ordering (parallel or series) method used.