Time to normalisation of C-reactive protein and incidence of relapse in microscopic polyangiitis: A medical records review study in Japan

Objectives Despite the identification of risk factors for relapses in antineutrophil cytoplasmic antibody-associated vasculitis, the relationship between changes in C-reactive protein (CRP) levels after the initial treatment and the incidence of relapse remains unknown. This study aimed to assess the association between the time taken for normalisation of CRP levels and the incidence of relapse in Japanese adult patients with microscopic polyangiitis. Methods This study included 85 consecutive patients with newly diagnosed microscopic polyangiitis who achieved remission after 6 months of immunosuppressive treatment at the Aichi Medical University Hospital between 2009 and 2017. The relationship between the time to normalisation of CRP after the initial immunosuppressive treatment and relapse incidences was evaluated using multivariable Cox proportional hazard models. Results During the follow-up period, 13 (30.2%), 7 (41.2%), and 16 (64.0%) patients relapsed (P = .025) within 1-14, 15-28, and >= 29 days of normalisation, respectively. The hazard ratios [95% confidence intervals (CIs)] for the time to normalisation of CRP of 1-14, 15-28, and >= 29 days were 1.00 (reference), 2.42 (95% CI: 0.92-6.39), and 3.48 (95% CI: 1.56-7.76), respectively. Conclusions A significant association between the time to normalisation of CRP and the relapse incidence in Japanese patients with microscopic polyangiitis was observed.