Anti-JC virus seroprevalence in a Spanish multiple sclerosis cohort: JC virus seroprevalence in Spain

To estimate the seroprevalence of anti-JCV antibodies, seroconverting rates and evolution of antibody levels in a multiple sclerosis (MS) Spanish cohort. Multicenter, retrospective cross-sectional and longitudinal study. The JCV seroprevalence was analyzed in 711 MS patients by using 1st (STRATIFY-1) and 2nd generation (STRATIFY-2) two-step ELISA over 2.65 (±0.97) years. Seroconversion rate was obtained over 2 samples from 314 patients, and index stability from 301 patients with 3 or more samples available. The effect of each ELISA generation, demographics, clinical characteristics and therapy on seroprevalence was assessed by logistic regression. The overall anti-JCV seroprevalence was 55.3% (51.6-58.9), similar across regions (p=0.073). It increased with age (p