Table 3. Diagnostic accuracy of anti-SARS-CoV-2 in the detection of past COVID-19 infection taking RT-PCR as the golden standard.
Sensitivity = TP/(TP+FN); Specificity = TN/(TN+FP); PPV=TP/(TP+FP); NPV = TN/(TN+FN); Likelihood ratio positive = sensitivity/(100 − specificity); Likelihood ratio negative = (100 − sensitivity)/specificity; Diagnostic accuracy = (TP+TN)/(TP+TN+FP+FN); PPV: positive predictive value; NPV: negative predictive value; POS-LR: positive likelihood ratio; NEG-LR: negative likelihood ratio; Diag accuracy: diagnostic accuracy.
| Anti-SARS CoV-2 antibody | RT-PCR for COVID-19 | Total | |
| Positive | Negative | ||
| Reactive | 94 (TP) | 3 (FP) | 97 (22.8%) |
| Non-reactive | 11 (FN) | 318 (TN) | 329 (72.2%) |
| Total | 105 | 321 | 426 |
| Sensitivity | =94/105 | =89.5% | |
| Specificity | =318/321 | =99.06% | |
| PPV | =94/97 | =96.90% | |
| NPV | =318/329 | =96.6% | |
| POS-LR | =89.5/100-99.06 | =95.21 | |
| NEG-LR | =100-89.5/99.06 | =0.1 | |
| Diag accuracy | =94+318/426 | =96.7% | |