Increased Rheumatoid Factor production in patients with severe COVID-19

Searching for Rheumatoid Factors (RF) in patients with coronavirus disease (COVID-19) has rarely been described. To investigate the association between RF isotypes (IgM, IgA, and IgG) and different clinical presentations of COVID-19 in a series of Tunisian patients. Eighty-two COVID-19 patients were enrolled in this study. Symptomatic cases were recruited from the Department of COVID-19 and the intensive care unit (ICU) of the University Hospital of Mahdia, Tunisia, from January 2021 to March 2021. Different RF isotypes were assessed using a commercial enzyme-linked immunosorbent assay (ELISA). Forty-one patients (50%) had RF of any isotype. Thirty-two patients (39%) were tested positive for RF-IgM. Symptomatic forms of the disease were associated with RF-IgM positivity (p = 0.005). The mean concentration of RF-IgM was higher in the severe form than in the moderate and asymptomatic forms (p = 0.006). Our study suggests that the production of RF-IgM isotype is increased in patients with severe COVID-19.