Evaluation of SARS-CoV-2 Specific Antibodies in Recovered Patients by Different ELISA Kits

Background: The coronavirus disease 2019 (COVID-19) was first reported in December 2019 in Wuhan, Hubei Province of China. As long as the 27th of December 2021, approximately 280 million people have been infected with coronavirus, resulting in more than 5,418,421 deaths worldwide. Since the beginning of the COVID-19 pandemic, different methods were introduced for diagnosing coronavirus-infected patients and evaluating the immune response, following the vaccination.Objective: The current study aimed to compare the level of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) specific IgG in a group of patients who recovered from COVID-19, measured by three different enzyme-linked immunosorbent assay (ELISA) kits.Methods: This cross-sectional study was conducted on sera from patients who recovered from a real-time reverse transcriptase-polymerase chain reaction (RT-PCR)-confirmed COVID-19 in Birjand, South Khorasan, Iran. SARS-CoV-2 anti-nucleocapsid (N) and spike (S) protein IgG levels were measured using commercial ELISA kits. Comparison between groups was made using one-way ANOVA and Tukey post hoc tests.Results: The mean titer of anti-N IgG was significantly higher for the PishtazTeb Diagnostics kit than the Ideal Tashkhis Atieh kit (p<0.05). There was no correlation between the titer of anti-N IgG (PishtazTeb Diagnostics and Ideal Tashkhis Atieh) and anti-S IgG (Chemobind Company) antibodies.Conclusion: This study indicates that the domestic ELISA kits have variable but acceptable sensitivity for detecting SARS-CoV-2 specific IgG antibodies.