6. Specificity by test method (IgG, IgM, total Ab).
| Target | Subgroup |
Test groups (true positives/COVID cases) Specificity (95% CI) |
||||
| Pre‐pandemic | Suspected of COVID‐19 |
Current RT‐PCR‐ negative |
Current untested | Other/mixed unclear | ||
| IgG | ELISA | 55 (9999/10,336) | 6 (585/609) | 4 (298/308) | 9 (739/745) | 9 (544/562) |
|
98.4 (97.7, 98.9) |
96.9 (92.5, 98.7) |
97.0 (91.9, 98.9) |
99.2 (98.2, 99.7) |
97.2 (94.1, 98.7) |
||
| CLIA | 55 (16,413/16,545) | 9 (640/661) | 11 (5854/5899) | 2 (820/829) | 3 (132/135) | |
|
99.5 (99.2, 99.7) |
97.2 (93.8, 98.8) |
99.3 (98.6, 99.7) |
98.9 (97.5, 99.5) |
98.0 (91.5, 99.6) |
||
| Lateral flow/CGIA/FIA | 68 (10,657/10,889) | 4 (271/299) | 14 (1087/1129) | 5 (955/987) | 15 (1393/1425) | |
|
98.7 (98.2, 99.1) |
90.7 (77.2, 96.5) |
97.3 (95.1, 98.5) |
97.5 (95.2, 98.7) |
98.5 (97.1, 99.2) |
||
| Comparison between groupsa | P < 0.001 | P = 0.172 | P = 0.01 | P = 0.099 | P = 0.452 | |
| IgM | ELISA | 14 (2743/2840) | 2 (206/213) | 2 (97/98) | 4 (617/620) | 2 (354/360) |
|
98.1 (95.7, 99.2) |
97.1 (81.6, 99.6) |
99.1 (92.3, 99.9) |
99.6 (98.3, 99.9) |
97.2 (87.6, 99.4) |
||
| CLIA | 10 (4232/4298) | 3 (79/84) | 4 (1471/1510) | 1 (583/586) | 1 (72/72) | |
|
99.2 (97.7, 99.7) |
96.1 (78.0, 99.4) |
98.1 (95.3, 99.2) |
99.5 (97.6, 99.9) |
99.7 (97.6, 100) |
||
| Lateral flow/CGIA/FIA | 58 (7398/7668) | 4 (247/300) | 14 (1084/1127) | 5 (945/989) | 18 (2424/2494) | |
|
98.3 (97.3, 98.9) |
80.9 (51.6, 94.4) |
97.1 (94.9, 98.4) |
97.2 (93.4, 98.9) |
97.1 (95.5, 98.1) |
||
| Comparison between groupsa | P = 0.412 | P = 0.205 | P = 0.436 | P = 0.075 | P = 0.048 | |
| IgG/IgM | ELISA | 6 (1269/1294) | ‐ | ‐ | 3 (316/320) | ‐ |
|
99.2 (95.9, 99.9) |
‐ | ‐ |
99.2 (94.9, 99.9) |
‐ | ||
| CLIA | 1 (40/40) | 2 (180/188) | ‐ | ‐ | 2 (304/307) | |
|
100b (91.2, 100)c |
97.3 (28.3, 100) |
‐ | ‐ |
99.3 (96.0, 99.9) |
||
| Lateral flow/CGIA/FIA | 60 (7180/7428) | 13 (1404/1477) | 7 (348/359) | 3 (389/393) | 18 (1505/1580) | |
|
98.5 (97.4, 99.2) |
99.3 (94.7, 99.9) |
96.9 (94.6, 98.3) |
99.2 (95.8, 99.8) |
96.7 (94.5, 98.0) |
||
| Comparison between groups | P = 0.397 | P = 0.578 | ‐ | P = 0.948 | P = 0.085 | |
| Total antibodies (Ab) | ELISA | 8 (2009/2020) | 1 (50/50) | ‐ | 1 (300/300) | 1 (97/100) |
|
99.6 (98.7, 99.9) |
100b (92.9, 100)c |
‐ |
100b (98.8, 100)c |
97.0b (91.5, 99.4)d |
||
| CLIA | 36 (9903/9931) | 3 (484/490) | 4 (364/364) | 2 (1029/1029) | 1 (26/26) | |
|
99.9 (99.7, 99.9) |
98.8 (97.3, 99.4) |
100b (99.0, 100)c |
100b (99.6, 100)c |
100b (86.7, 100)c |
||
| Lateral flow/CGIA/ FIA | ‐ | ‐ | ‐ | ‐ | ‐ | |
| ‐ | ‐ | ‐ | ‐ | ‐ | ||
| Comparison between groups | P = 0.183 | ‐ | ‐ | P = 0.948 | ‐ | |
CI: confidence interval CGIA: colloidal gold immunoassay CLIA: chemiluminescent immunoassay ELISA: enzyme linked immunosorbent assay FIA: fluorescence immunoassay RT‐PCR: reverse transcription polymerase chain reaction
aP values were generated using the likelihood ratio test comparing the model for each reference standard group including a covariate for test method to the model without the covariate
bEstimates and confidence intervals by summing the counts of true positive and false negative across 2 x 2 tables
c97.5% one‐sided exact binomial confidence interval
d95% exact binomial confidence interval