Table 1. Analytical performance of IgM and IgG ELISA in detecting Lassa virus-specific antibodies in 576 serum samples from a Lassa fever endemic area in Nigeria using IFA as a reference method.
| Serological status defined by IFA | Type of IgG ELISA | Performance of ELISA vs. IFA | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| True pos, n | False pos, n | True neg, n | False neg, n | Specificity, % | Sensitivity, % | PPV, % | NPV, % | Accuracy, % | ||
| IgM+ | None | 188 | 14 | 339 | 35 | 96.0 | 84.3 | 93.1 | 90.6 | 91.5 |
| IgG+ | RF | 228 | 15 | 308 | 25 | 95.4 | 90.1 | 93.8 | 92.5 | 93.1 |
| CD32 | 227 | 15 | 308 | 26 | 95.4 | 89.7 | 93.8 | 92.2 | 92.9 | |
| IgM+ / IgG– | RF | 3 | 15 | 537 | 21 | 97.3 | 12.5 | 16.7 | 96.2 | 93.8 |
| CD32 | 3 | 18 | 534 | 21 | 96.7 | 12.5 | 14.3 | 96.2 | 93.2 | |
| IgM–/ IgG+ | RF | 39 | 20 | 502 | 15 | 96.2 | 72.2 | 66.1 | 97.1 | 93.9 |
| CD32 | 41 | 20 | 502 | 13 | 96.2 | 75.9 | 67.2 | 97.5 | 94.3 | |
| IgM+ / IgG+ | RF | 174 | 10 | 367 | 25 | 97.3 | 87.4 | 94.6 | 93.6 | 93.9 |
| CD32 | 171 | 10 | 367 | 28 | 97.3 | 85.9 | 94.5 | 92.9 | 93.4 | |
Abbreviations: ELISA enzyme-linked immunosorbent assay; IFA, immunofluorescence assay; NPV, negative predictive value; PPV, positive predictive value; RF, rheumatoid factor.