Table 1.
Characteristics of the study population and the specimens.
| Variables | Total | COVID-19 patients | HCWs (Negative controls) | |
|---|---|---|---|---|
| Residential care center | Designated hospitals | |||
| Number of specimens (patients) | 483 (237) | 61 (61) | 296 (50) | 126 (126)* ‡ |
| Age, years | 52.0 (30.0–71.0) | 27.0 (24.0–37.0) | 70.0 (61.0–74.0) | 33.5 (27.0–42.0) |
| Sex, male: female | 75:162 | 25:36 | 23:27 | 27:99 |
| Time point | ||||
| Seroconverted (≥ 14 days)† | 279 (110) | 61 (61) | 218 (49) | NA |
| Acute (< 21 days)‡ | 151 (41) | 0 (0) | 151 (41) | NA |
| Convalescent (≥ 21 days)‡ | 206 (101) | 61 (61) | 145 (40) | NA |
| Severity of illness | ||||
| Mild-to-moderate (FiO2 < 60%) | 206 (89) | 61 (61) | 145 (28) | NA |
| Severe-to-critical (FiO2 ≥ 60%) | 151 (22) | 0 (0) | 151 (22) | NA |
Data are expressed as the number of specimens (patients) or as medians (IQR), unless indicated otherwise. *While all the sera of COVID-19 patients underwent PRNT, 33 of 126 sera of HCWs underwent PRNT. †For calculating the analytical performance in discriminating SARS-CoV-2 infection, sero-converted sera of COVID-19 patients were used as positive specimens and all the sera of HCWs were used as negative controls. ‡For the investigation of titer correlation between immunoassay kits and PRNT, all specimens of COVID-19 patients were used, and subgroup analyses were conducted according to the acute/convalescent phase.
COVID-19, coronavirus disease 2019; HCW, healthcare worker; FiO2, fraction of inspired oxygen; PRNT, plaque reduction neutralization test.