Sensitivity and specificity of different immunoassays to detect antibodies against severe acute respiratory syndrome coronavirus 2
| Type of immunoassay# | Sensitivity | Specificity¶ | ||||
| Patients n | Positive n | % (95% CI) | Uninfected n | Negative n | % (95% CI) | |
| Ab | ||||||
| ELISA-Ab | 80 | 78 | 97.5 (91.3–99.7) | 300 | 300 | 100.0 (98.8–100.0) |
| CMIA-Ab | 80 | 77 | 96.3 (89.4–99.2) | 300 | 298 | 99.3 (97.6–99.9) |
| LFIA-Ab | 80 | 78 | 97.5 (91.3–99.7) | 209 | 199 | 95.2 (91.4–97.7) |
| Combined | 80 | 79 | 98.8 (93.2–100.0) | 209 | 197 | 94.3 (90.2–97.0) |
| IgM | ||||||
| ELISA-IgM | 80 | 74 | 92.5 (84.4–97.2) | 300 | 300 | 100 (98.8–100) |
| CMIA-IgM | 80 | 69 | 86.3 (76.7–92.9) | 300 | 298 | 99.3 (97.6–99.9) |
| LFIA-IgM | 80 | 71 | 88.8 (79.7–94.7) | 209 | 205 | 98.1 (95.2–99.5) |
| Combined | 80 | 75 | 93.8 (86.0–97.9) | 209 | 203 | 97.1 (93.9–98.9) |
| IgG | ||||||
| ELISA-IgG | 80 | 71 | 88.8 (79.7–94.7) | 100 | 100 | 100.0 (96.4–100.0) |
| LFIA-IgG | 80 | 69 | 86.3 (76.7–92.9) | 209 | 208 | 99.5 (97.4–100.0) |
| Combined | 80 | 75 | 93.8 (86.0–97.9) | 100 | 99 | 99.0 (94.6–100) |
Ab: total antibody; CMIA: chemiluminescence microparticle immunoassay; LFIA: lateral flow immunoassay. #: the combined sensitivities were calculated based on positive findings by any of the assays; the combined specificities were calculated based on negative findings for all assays. ¶: none of the controls reported close contact with any confirmed coronavirus disease 2019 patients, and individuals who were positive for any of the antibody tests were tested to be PCR negative with sputum or saliva samples collected later. With the very limited local community spread of the virus during the period in mind, and for more rigorous evaluation of an assay's specificity, the community controls with positive results in antibody assays were considered false-positive.