Correlation of Anti SARS-CoV-2 Antibodies Development with Clinical Severity in PCR Confirmed COVID Cases

Abstract

Objective: The aim of this study is to evaluate the anti SARS-CoV-2 antibodies isotypes and their concentration in PCR confirmed COVID cases and their correlation with clinical severity.

Methodology: A prospective, cross sectional study was conducted from April to July 2020 in Karachi. 256 participants of different disease severity were tested for the presence of anti SARS-CoV-2 IgG, IgM and IgA antibodies performed by quantitative Enzyme linked Immunosorbant Assay (ELISA). Mean and standard deviation (SD) for quantitative variables and frequency / percentage for categorical variables was calculated.  For quantitative ELISA, antibody titre was taken in U/mL.

Results: Overall mean number of days since the diagnosis of COVID-19 till the sample was collected is 22.9±16.7 days. All patients were categorized into four groups; 137 (53.5%), 75 (29.3%), 36 (14.1%) and 8 (3.1%) in mild, moderate, severe and critical groups respectively. Out of 137 mild cases, IgG was found in 74 (54%) and IgA in 28 (20.4%) cases. In moderate group of 75 patients, IgG was found in 57 (76%), IgA in 49 (65.3%) and IgM in 35 (46.6%). 36 severe patients had IgG& IgA in 27 (75%) each and IgM in 19 (52.7%) cases. In critical group, 5 (62.5%) had IgG & IgM while 7 (87.5%) had IgA.

Conclusion: Antibody kinetics is quite complex and requires detailed investigation among the patients of varying disease severity. Further studies are needed to assess humoral responses in achieving herd immunity.