COVID-19 symptom duration predicts immunoglobulin G seropositivity

The study focused on the relationship between routine clinical characteristics and anti-SARS-CoV-2 specific antibodies in a pilot sample of healthcare workers (HCWs) having suffered COVID-19. The aim was to investigate the existence of readily available predictors of antibodies against COVID-19.

As part of the recognition of COVID-19 as an occupational disease in 152 HCWs with the mean age of 43.2 years, personal, anthropometric and anamnestic data related to the disease as well as anti-spike immunoglobulin (Ig) levels were obtained. Through descriptive statistics, correlation and regression analyses, relationships of all variables and Ig levels, especially seropositivity of IgG, were investigated.

The mean interval between the symptom onset and the determination of antibodies was 58 days. IgG seropositivity and IgM seropositivity were noted in 82 % and 49 % of HCWs, respectively. Symptom duration was the only statistically significant predictor of IgG seropositivity. With each day of symptom duration, the probability of IgG seropositivity increased from 1.078 to 1.092 times (p < 0.05). If symptoms lasted longer than 17 days, a majority (almost 80 %) of the subjects demonstrated seropositivity in the following months.  CONCLUSION: The presence of IgG immunity may be assumed from symptom duration. Such easy recognizing of seropositive patients may be a useful tool, e.g. in vaccination strategies (Tab. 3, Fig. 1, Ref. 28).