Autoimmune diseases drive biological false-positive syphilis serology: A retrospective cohort of 35,995 tests.

To analyze the related factors that may cause the biological false-positive (BFP) reaction of syphilis screening test, with a particular focus on the correlation between autoimmune diseases and the biological false-positive results of syphilis screening test. This study aims to provide insights into the mechanisms underlying BFP reactions in autoimmune diseases and to improve the accuracy of syphilis serological diagnosis. We conducted a retrospective review of 35,995 individuals who underwent syphilis screening at Guangzhou First People's Hospital from 2016 to 2023. The clinical characteristics including age, gender, and underlying diseases were compared between patients with BFP and those with a negative result of syphlilis screening test. The differences in autoantibody profiles and anticardiolipin antibody detection results of BFP patients and negative groups were analyzed. The observed incidence rate for biological false-positive reactions was 0.78 %, among which 96.7 % of cases exhibited relatively low titers (≤1:4). Significant differences in BFP responses were observed across different age groups (P < 0.05). In the false positive group, the positive rates of anti-double-stranded DNA antibody (ds-DNA), anti-ribosomal antibody (rRNP), soluble substance A (SSA), anti-Sm antibody (Sm), anti-ribonucleoprotein antibody (nRNP), histone, anti-nucleosome antibody (AauA), centromere antibody (CENP B), and antinuclear antibody (ANA) were significantly higher compared to the negative group (P < 0.05). Autoimmune diseases and specific autoantibodies are key contributors to syphilis BFP reactions. Incorporating autoimmune testing may improve screening accuracy.