Table 2 Connecting sensitivity, specificity, and prevalence, to predictive values and NNT values
From: Planning clinically relevant biomarker validation studies using the “number needed to treat” concept
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Sensitivity | 0.50 | 0.60 | 0.70 | 0.80 | 0.90 | 1.00 | |
Specificity | 0.50 | 0.60 | 0.70 | 0.80 | 0.90 | 1.00 | |
PPV | 0.50 | 0.60 | 0.70 | 0.80 | 0.90 | 1.00 | Prevalence = 0.5 (see Fig. 3a) |
NPV | 0.50 | 0.60 | 0.70 | 0.80 | 0.90 | 1.00 | Prevalence = 0.5 (see Fig. 3a) |
NNT Pos | 2.0 | 1.7 | 1.4 | 1.3 | 1.1 | 1.00 | Prevalence = 0.5 (see Fig. 3a) |
NNT Neg | 2.0 | 2.5 | 3.3 | 5.0 | 10.0 | Inf | Prevalence = 0.5 (see Fig. 3a) |
PPV | 0.05 | 0.07 | 0.11 | 0.17 | 0.32 | 1.00 | Prevalence = 0.05 (see Fig. 3b, c) |
NPV | 0.95 | 0.97 | 0.98 | 0.99 | 0.99 | 1.00 | Prevalence = 0.05 (see Fig. 3b, c) |
NNT Pos | 20.0 | 13.7 | 9.1 | 5.8 | 3.1 | 1.00 | Prevalence = 0.05 (see Fig. 3b, c) |
NNT Neg | 20.0 | 29.5 | 45.3 | 77.0 | 172.0 | Inf | Prevalence = 0.05 (see Fig. 3b, c) |
