Comparing the molecular and serological testing for detection of SARS - COV-2

The exact protective antibody to the SARS- CoV-2 is still unknown. This study aimed to compare molecular and serological testing for the diagnosis of Covid-19.

In this study, a total of 100 participants, 50 patients with confirmed SARS-CoV-2 infection using real-time reverse transcriptase PCR (RT-PCR) and 50 controls with negative RT-PCR test, were enrolled. The serum level of IgM and IgG antibodies against nucleocapsid antigens of SARS-CoV-2 were tested using the enzyme-linked immunosorbent assays (ELISAs) and also antibodies were tested again after four months in the case group. This study was carried out in the Asadabadei clinic between April and June 2020.

The Seroconversion rates of IgM in the case and control groups were 14% and 4%, respectively, but the differences were not statistically significant (P =0.134). In the case group, the Seroconversion rate of IgG was significantly higher than the control group (44% vs. 4%) (P <0.001).

Our results revealed that IgM antibodies in the diagnosis of Covid -19, especially in the early stages of the disease have less diagnostic value compared to PCR. It seems that periodic follow-up of serological tests is necessary to know the production of appropriate antibody response in Covid-19 patients as well as in receiving the vaccine.