Table 3.
Proposed immunologic criteria for the diagnosis of the stage of the disease
| Test results | Clinical significance | ||
|---|---|---|---|
| PCR | IgM | IgG | |
| + | − | − |
Proposed immunologic period of infection before the symptoms develop Early days of infection before detectable antibody response Antibody assay may have given false‐negative results |
| + | + | − | Early stage of infection approximately 5‐7 d after the beginning of symptoms |
| + | + | + | Active phase of infection |
| + | − | + |
Late phase or recurrent infection IgM ELISA is false‐negative |
| − | + | − |
Early stage of infection IgG may be false‐negative RT‐PCR result may be false‐negative |
| − | − | + |
Past infection Recovered PCR‐negative patients Cross‐reactivity with other coronaviruses |
| − | + | + |
Recovery stage of infection Early infection with false‐negative RT‐PCR |