Figure 2.

Replicate assays improve efficacy estimation. Characteristics of majority rule and confirmatory majority rule strategies, as functions of the number of replicate assays, are used. The majority and confirmatory majority rules, plotted in red and blue, use the same assay for each replicate. The confirmatory majority rule, plotted in green, uses a more sensitive (smaller FN) and less specific (higher FP) initial assay; subsequent replicates are all the same. Increasing the number of replicates for all strategies reduces the false-positive rate (top row), but the confirmatory strategy exhibits a higher false-negative rate unless a more sensitive initial assay is used (middle row). Since the dilution effect depends, primarily, on false positives, all strategies can achieve reductions in efficacy dilution (bottom row). Parameters: Incidence TIP = 0.02. Majority rule and confirmatory majority rule: FP = 0.01 (left column), 0.05 (right column); FN = 0.2. For confirmatory majority rule with sensitive initial assay, the initial assay has 4-fold reduction in false-negative rate and 4-fold increase in false-positive rate: FP for the first assay = 0.04 (left column), 0.2 (right column); FN for the first assay = 0.05. Note that, for a single replicate (1 on the x-axis), the value plotted is just that of a single assay, and the difference between the “sensitive initial value” result and others is only due to the different characteristics assumed for that assay.