SARS-CoV-2 infection is not associated with the emergence of monoclonal gammopathies

Background: Upon infection activated plasma cells produce large quantities of antibodies which can lead to the emergence of a monoclonal component (MC), detectable by serum protein electrophoresis (SPEP). This study aims to investigate any correlation between SARS-CoV-2 infection and MC development and, if identified, whether it persists during follow-up.Methods: SPEPs of 786 patients admitted to hospitals between March 01 2020 and March 31 2022 were evaluated. Positive (SARS-CoV-2+) and negative (SARS-CoV-2-) patients to nasopharyngeal swab for SARS-CoV-2 by RT-PCR were included. The persistence/new occurrence of MC was investigated for all patients during follow-up. Patient groups were compared by chi-square analysis.Results: MC was identified in 12% of all patients admitted to hospital, of which 28.7% were SARS-CoV-2+. The most common immunoglobulin isotype in both groups was IgG-k. There was no correlation between MC development and SARS-CoV-2 infection (p = 0.173). Furthermore, the risk of MC persistence in SARS-CoV-2-negative patients was revealed to be higher than in the SARS-CoV-2+ at follow-up (HR = 0.591, p = 0.05).Conclusions: Our study suggests that the detection of MC during SARS-CoV-2 infection is most likely due to the hyperstimulation of the humoral immune system, as also occurs in other viral infections.