Background False positive result of syphilis test is a characteristic finding in patients with systemic lupus erythematosus (SLE), especially combined with antiphospholipid syndrome (APS). We evaluated the clinical characteristics in SLE patients who showed the false positive result of syphilis test.

Methods Patients who were tested for syphilis screening test at SLE diagnosis in Severance Hospital between January 2006 and December 2016 were included in this study. The baseline characteristics and clinical outcomes were compared between patients with false positive result of syphilis test and negative result of syphilis.

Results Of 145 patients included in this study, 20 (13.8%) patients showed the false positive result of syphilis test. At SLE diagnosis, patients with negative syphilis result had higher SLE disease activity index (5.0 vs 8.0, p<0.001), and were more commonly complicated with nephritis (15.0% vs 41.6%, p=0.026). Low disease activity, high protein level, and presence of APS antibodies were independently associated with the false positive result of syphilis test (p=0.030, 0.014 and 0.002, respectively). Although the thrombotic risk was significantly higher in patients with false positive syphilis result (p=0.041), the overall mortality showed no difference between patients with false positive result and negative result of syphilis test.

Conclusions Clinical characteristics of SLE patients with false positive result of syphilis test showed lower disease activity at SLE diagnosis, but comparable overall survival and higher thrombotic risk.

Funding Source(s): None