Abstract
Patients with chronic inflammatory diseases are often treated with immunosuppressants and therefore are of particular concern during the SARS-CoV-2 pandemic. Serological tests will improve our understanding of the infection and immunity in this population, unless they tests give false positive results. The aim of this study was to evaluate the specificity of SARS-Cov-2 serological assays using samples from patients with chronic inflammatory diseases collected prior to April 2019, thus defined as negative. Samples from patients with multiple sclerosis (MS, n=10), rheumatoid arthritis (RA, n=47) with or without rheumatoid factor (RF) and/or anti-cyclic citrullinated peptide antibodies (anti-CCP2) and systemic lupus erythematosus (SLE, n=10) with or without RF, were analyzed for SARS-CoV-2 antibodies using 17 commercially available lateral flow assays (LFA), two ELISA kits and one in-house developed IgG multiplex bead-based assay. Six LFA and the in-house validated IgG assay correctly produced negative results for all samples. However, the majority of assays (n=13), gave false positive signal for samples from patients with RA and SLE. This was most notable in samples from RF positive RA patients. No false positive samples were detected in any assay using samples from patients with MS. Poor specificity of commercial serological assays could possibly be, at least partly, due to interfering antibodies in samples from patients with chronic inflammatory diseases. For these patients, the risk of false positivity should be considered when interpreting results of the SARS-CoV-2 serological assays.
Highlights
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative agent of the coronavirus disease 2019 (COVID19), which emerged as a pandemic late 2019 [1]
For the 17 lateral flow assays (LFA) evaluated for specificity using 25 rheumatoid arthritis (RA) samples that were positive for rheumatoid factor (RF), 10 assays had unspecific signal detected for at least one immunoglobulin isotype (Figures 2 and 3)
In the case of SARS-CoV-2, it seems that a small proportion of the individuals who have been infected do not develop antibodies, at least not as determined by currently available serological assays [29]
Summary
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative agent of the coronavirus disease 2019 (COVID19), which emerged as a pandemic late 2019 [1]. 6% of the world’s population are affected by chronic inflammatory diseases which includes conditions such as multiple sclerosis (MS), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) [7]. These are generally progressive diseases and for the majority there are no cures, treatment is centered around slowing disease progression with immunomodulatory treatments. RF is detected in approximately 70% of RA patients, the presence of RF is not specific for RA These autoantibodies are present in a variety of other diseases as well as in the general population and may increase with age, smoking and chronic infection [10, 11]. 25% of SLE patients have RF [13], but these patients can have anti-nuclear antibodies (ANA) and antidouble-stranded (ds) DNA antibodies
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