Table 1.
Background of patients with antibody test results at the timing of initial RT-PCR diagnosis.
| PCR positive | PCR negative | ||
|---|---|---|---|
| (n = 12) | (n = 6) | ||
| Age, IQR | 61 (51.5–72.5) | 56 (41–78) | P = 1.00 |
| Gender (male/female) | 9/3 | 3/3 | P = 0.34 |
| Severity of COVID-19a | |||
| Asymptomatic | 2 (16.7%) | – | |
| Mild | 7 (58.3%) | – | |
| Moderate | 2 (16.7%) | – | |
| Severe | 1 (8.3%) | – | |
| Days after onsetb | 4 (0–10) | – | |
| Ct values of PCR | |||
| N1 gene | 22.4 (17.0–42.9) | – | |
| N2 gene | 14.6 (9.0–30.0) | – | |
| Immunosuppression | |||
| Steroid use | 0 (0.0%) | – | |
| Immunosuppressant use | 1 (8.3%) | – | |
| Diabetes mellitus | 0 (0.0%) | – | |
| Cancer chemotherapy | 1 (8.3%) | – | |
| ALLTest IgM | 2/10b | 0/6b | P = 0.53 |
| IgG | 1/11b | 0/6b | P = 1.00 |
| SD BIOSENSOR IgM | 1/11b | 0/6b | P = 0.53 |
| IgG | 2/10b | 0/6b | P = 1.00 |
| KURABO IgM | 0/12b | 0/6b | – |
| IgG | 2/10b | 0/6b | P = 0.53 |
| Quantitative antibody test (iFLASH) | |||
| IgM | 1/11b | 0/6b | |
| IgM titre (AU/mL, IQR) | 0.71 (0.36–0.86) | 0.24 (0.19–0.47) | P = 0.62 |
| IgG | 3/9b | 0/6b | |
| IgG titre (AU/mL, IQR) | 1.10 (0.76–6.33) | 0.40 (0.37–0.69) | P = 0.13 |
aThe severity at the timing of diagnostic PCR performance is shown. Definition of severity is as follows: ‘mild’ for symptomatic patients without hypoxia, ‘moderate’ for symptomatic patients with hypoxia requiring oxygen inhalation and ‘severe’ for symptomatic patients with hypoxia requiring mechanical ventilation.
bFor symptomatic patients, the onset date was defined as the date on which symptom of COVID-19 or radiographic abnormality related to COVID-19 appeared. For asymptomatic patients without significant radiographic abnormality, the onset date was defined as the date on which the initial PCR positivity was confirmed. Antibody test results at the timing of initial RT-PCR diagnosis are displayed as follows: number of positive test results/number of negative test results.