To determine the predictive value of disease characteristics at 12-month follow-up after the diagnosis of GPA for subsequent relapses in a cohort of patients followed at a tertiary vasculitis clinic.
Demographic, clinical, and biological data at diagnosis and during follow-up from patients with GPA followed for at least 24 months at the Mount Sinai Hospital Vasculitis Clinic in Toronto, Canada were extracted from the Canadian Vasculitis Research Network (CanVasc) database and analyzed. The association between ANCA status and type (PR3- or MPO-ANCA), presence of microscopic hematuria, or serum creatinine level at follow-up month 12 ± 3 (M12) and relapses after M12 were assessed using Cox proportional hazard models.
A total of 113 GPA patients were included in this study (50 ANCA positive, 63 ANCA negative at M12). Patient demographics and disease characteristics were similar at diagnosis, including the treatments used for induction and at M12. The global 5-year relapse rate was 55.8%, without any difference in the relapse rates after M12 between those ANCA-positive or negative at M12. However, in multivariate analyses, MPO-ANCA positivity at M12 was predictive of increased relapses after M12 (hazard ratio [HR] 3.54, P=0.01), as was the presence of microhematuria at M12 (HR 1.91, P=0.04). In contrast, higher serum creatinine levels at M12 were associated with a decreased risk of subsequent relapse (HR 0.99, P=0.04).
In this cohort of patients with GPA, MPO-ANCA positivity and persistent microscopic hematuria at M12 were associated with increased risk of subsequent relapse, and could thus have value to predict disease outcome during follow-up.