Anti-RNA polymerase III antibodies (anti-RNAP III) have been reported as potential immune markers of Systemic Sclerosis (SSc). Until now, their clinical use was disregarded because of technical difficulties to perform immunoprecipitation. Recently, ELISA kits became commercially available allowing an easy detection of anti-RNAP III. We intended to clarify the relevance of these antibodies in the diagnosis of SSc by ELISA detection.
The prevalence of anti-RNAP III was analyzed using two ELISA kits in 50 consecutive SSc patients from Marseilles in South of France. Controls included 66 patients with other systemic autoimmune diseases, 34 viral diseases and 50 healthy subjects. Positive results with at least one ELISA kit were controlled by immunoprecipitation which is the reference assay.
In this study, positivity for anti-centromere and/or anti-topoisomerase I antibodies was observed in 84% of SSc patients. The prevalence of anti-RNAP III in SSc patients was 0% to 6% (3/50) depending on the ELISA kit and only 2% by immunoprecipitation. Concerning controls, two rheumatoid arthritis patients were positive using ELISA (6%), including one with immunoprecipitation confirmation. No anti-RNAP III was detected in systemic lupus erythematosus patients. Three blood donors and one viral disease control were positive using ELISA, but all were negative by immunoprecipitation.
Anti-RNAP III was rarely detected in a French population of SSc patients. Their prevalence was even lower than the one observed in rheumatoid arthritis controls. Therefore local immunologic profiles should be established before deciding a change in clinical practice for SSc immune screening.