Table 4 Diagnostic testing accuracy characteristics.
From: Evaluation of hepatitis C virus antibody assay using dried blood spot samples
Disease present | Disease not present | Total | |
|---|---|---|---|
Plasma anti-HCV+ | Plasma anti-HCV− | ||
DBS test result | Anti-HCV modified assay file | ||
Positive | 144 (TP) | 0 (FP) | 144 (TP + FP) |
Negative | 0 (FN) | 104 (TN) | 104 (TN + FN) |
Total | 144 (TP + FN) | 104 (TN + FP) | 248 |
Sensitivity = TP/(TP + FN) = 144/144 × 100% = 100% (95% CI 97.47–100.00) | |||
Specificity = TN/(TN + FP) = 104/104 × 100% = 100% (95% CI 96.52–100.00) | |||
Positive predictive value (PPV) = TP/(TP + FP) = 144/144 × 100% = 100% (95% CI 97.40–100.00), calculated at 58.06% prevalence (144 positive/248 total) | |||
Negative predictive value (NPV) = TN/(TN + FN) = 104/104 × 100% = 100% (95% CI 96.44–100), calculated at 58.06% prevalence | |||
Positive likelihood ratio (LR+) = sensitivity/(1-specificity) = NA | |||
Negative likelihood ratio (LR−) = (1-sensitivity)/specificity = 0 Area under the ROC curve (AUC) = 1.00 | |||
DBS test result | Anti-HCV on-market assay file | ||
Positive | 131 (TP) | 0 (FP) | 131 (TP + FP) |
Negative | 13 (FN) | 104 (TN) | 117 (TN + FN) |
Total | 144 (TP + FN) | 104 (TN + FP) | 248 |
Sensitivity = TP/(TP + FN) = 131/(131 + 13) × 100% = 90.97% (95% CI 85.06–95.11) | |||
Specificity = TN/(TN + FP) = 104/104 × 100% = 100% (95% CI 96.52–100.00) | |||
Positive predictive value (PPV) = TP/(TP + FP) = 131/131 × 100% = 100% (95% CI 97.22–100.00), calculated at 58.06% prevalence | |||
Negative predictive value (NPV) = TN/(TN + FN) = 104/(104 + 13) = 88.89% (95% CI 81.75–93.95), calculated at 58.06% prevalence | |||
Positive likelihood ratio (LR+) = sensitivity/(1-specificity) = NA | |||
Negative likelihood ratio (LR−) = (1-sensitivity)/specificity = (1–0.9097)/1 = 0.09 (95% CI 0.05–0.15) Area under the ROC curve (AUC) = 1.00 | |||
