Role of serology tests in COVID-19 non-hospitalized patients: A cross-sectional study

Severe acute respiratory syndrome coronavirus (SARS-CoV2) has imposed catastrophic impressions on the world. After all the focused researches conducted in the COVID-19 area, many features remain obscure. We have surveyed 1,363 outpatients with suspected COVID-19 in Tehran, Iran. The analysis emphasized on characteristics of patients with positive PCR or serology of SARS-CoV-2.

The nasopharyngeal swabs were tested for SARS-CoV2 PCR. Serum specimens were tested for SARS-CoV2 IgG and IgM. Clinical presentations of the patients, history of chronic diseases or drug use, contact with a possible COVID-19 patient and previous infection with SARS-COV2 were investigated.

Of the total 1,363 investigated patients, 22% had positive SARS-CoV-2 PCRs, 82% had positive IgG, 38% had positive IgM, and 31% had both positive IgM and IgG values. Positive serologic tests were significantly associated with a positive PCR test obtained previously in the course of the current disease (P value<0.001). IgG and IgM antibody values were significantly associated with underlying disease, cough, fever, chills, fatigue, and myalgia (all P values <0.001). Dyspnea was significantly associated with IgG levels (P value = 0.01), yet it was not associated with IgM serology (P value = 0.2). Positive serology tests were not associated with symptoms of coryza. GI symptoms were not associated with positive IgG test (P value = 0.1), yet it did show an association with positive IgM test (P value = 0.02). Cough, fever, chills, myalgia fatigue, dyspnea, and GI symptoms were all significantly associated with positive PCR (all P values <0.001), and symptoms of coryza did not show a significant relationship (P value = 0.8).

Assessing antibody titers in outpatients is invaluable due to the epidemiological importance of investigations in mild or even asymptomatic cases. Since the number of such studies in non-hospitalized patients is not high, the current study can be used as a comparison model.