Spread of SARS-CoV-2 infection is much greater than that captured with swab diagnostics

The actual prevalence of COVID-19 is still unknown due to the high proportion of subclinical infections. Measuring seroprevalence can be crucial in improving knowledge about the impact of COVID-19 in rheumatic patients. Data shared at EULAR 2021 Congress highlights that the spread of SARS-CoV-2 infection is far greater than that seen by capturing only COVID-19 cases diagnosed by swab, but consistent with a healthy population .

As part of the MAINSTREAM project, Favalli and his colleagues conducted a cross-sectional seroprevalence study between May 4 and June 16, 2020 to estimate the prevalence of anti-SARS-CoV-2 antibodies in a large cohort of people with rheumatoid arthritis (PR) or spondyloarthritis (SpA) treated with targeted biological or synthetic disease-modifying anti-rheumatic drugs (b / tsDMARDs) in a high COVID-19 endemic area (Lombardy, Italy). During this time, 300 people were tested for IgG, IgM, and IgA antibodies against three viral antigens: nucleoprotein, spike protein, and receptor binding domain. These data were compared with those observed in the healthy population during the same period and in the same region. All participants also completed a questionnaire to collect information on symptoms compatible with COVID-19, risk factors, and comorbidities.

Overall, 65% of participants suffered from RA, 23% from psoriatic arthritis, and 21% from ankylosing spondylitis. Most people were treated with tumor necrosis factor inhibitors (TNFi; 57%) and the rest were receiving abatacept (20%), interleukin 6 inhibitors (IL-6i; 11%) or januskinase inhibitors (JAKi; 5%). Of the 300 people, 4 had a previous diagnosis of COVID-19 defined by nasopharyngeal swab.

The immunoglobulin titers were evaluated and gave 9%, 13.6% and 13.3% of patients positive for IgG, IgM and IgA, respectively, and there was no significant difference from the population. in good health. Of the seropositive patients, 55.3% were asymptomatic, 16% had minor symptoms and 19.6% major, 7.1% were hospitalized. There were no deaths or admission to intensive care. Titers of IgM, IgG and IgA to the receptor binding domain of the virus were higher in patients with both minor and major symptoms compared to asymptomatic patients. No difference was found between seronegative and seropositive patients with regard to age, sex, rheumatic diagnosis and treatment with DMARD cs- and b / ts or corticosteroids. An increased relative risk was associated with obesity and the presence of at least two comorbidities.

This study confirms that, even in a cohort of rheumatic patients, the spread of SARS-CoV-2 infection is much greater than that seen by capturing only cases of COVID-19 diagnosed by swab. The underlying rheumatic disease and current treatment with b / ts DMARD do not appear to have an impact on the positivity of SARS-CoV-2 antibodies, which conversely appears to be associated with symptomatic COVID-19 and presence of comorbidities.

Provided by the European Alliance of Rheumatology Associations