High prevalence of false positive SARS-CoV2 serology in a cohort of patients with liver autoimmune diseases

Aim: Monitoring the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) immunization in patients with autoimmune diseases is of particular concern to understand their response to the infection and to the vaccine. In fact, the immunological disorder and the immunosuppressive therapies could affect the serological response. SARS-CoV2 serological tests potentially provide this information, although they were rapidly commercialized with internal verifications. Here, we analysed the seroprevalence to SARS-CoV2 in a cohort of patients with liver autoimmune diseases. Methods: From May to December 2020, a cohort of patients affected by primary biliary cholangitis (PBC), autoimmune hepatitis (AIH) and PBC/AIH overlap syndrome were screened with reverse transcription-polymerase chain reaction (RT-PCR) of nasopharyngeal swabs, rapid antigenic test and chemiluminescent serological test during routine follow-up. Results: The analysis of 42 patients was carried out: 18 (42.85%) PBC, 12 (28.57%) AIH and 12 (28.57%) PBC/AIH overlap syndromes. Only 2 patients (4.76%) resulted positive to the RNA, antigen and antibody detection tests, hence affected by SARS-CoV2 infection. 14 subjects out of 40 negative cases presented a positive serology for SARS-CoV2 antibodies, hence with a false positivity in the 35% of cases without infection. Notably, among these, 6 (42.86%) patients presented only immunoglobulin (Ig)M positivity, 6 (42.86%) patients presented positivity for only IgG and 2 (14.28%) patients were positive to both IgM and IgG. Notably, the presence of autoantibodies did not correlate with the serological false positivity, highlighting that there is no cross-reactivity with autoantibodies. Moreover, the presence of polyclonal hypergammaglobulinemia did not interfere with the serological test as its prevalence is not different between negative and false positive cases. Interestingly, the patients with false positive serology showed higher levels of gamma-glutamyltransferase (GGT) and C-reactive protein (CRP). Conclusions: Patients with liver autoimmune diseases present a high rate of false positive SARS-CoV2 serology. Therefore, new strategies are needed to study the serological response in this patient category.