Lower Myeloperoxidase-ANCA Titres at Diagnosis Are Associated with End-Stage Kidney Disease Progression During Follow-Up in Rituximab-Treated Patients with Microscopic Polyangiitis.

Background and

Objectives

To investigate whether myeloperoxidase (MPO)-antineutrophil cytoplasmic antibody (ANCA) titres at diagnosis are associated with the risk of end-stage kidney disease (ESKD) progression in patients with microscopic polyangiitis (MPA) treated with rituximab. Materials and

Methods

This retrospective cohort study included 34 patients with MPA who received rituximab. Clinical data, including MPO-ANCA titres at diagnosis and ESKD progression during follow-up, were assessed. Receiver operating characteristic (ROC) curve analysis was performed to assess whether MPO-ANCA titres could predict ESKD progression. The optimal cut-off value of MPO-ANCA titres was determined where the sum of sensitivity and specificity was at a maximum. Based on this cut-off value, patients were categorised into two groups, and the relative risk (RR) of ESKD progression was estimated.

Results

During a median follow-up of 39.5 months, seven patients (20.6%) progressed to ESKD. ROC curve analysis showed a significant inverse association between MPO-ANCA titres and ESKD progression (AUC 0.254, 95% confidence interval [CI] 0.046, 0.462 p = 0.048). The optimal cut-off of MPO-ANCA titres was 81.0 IU/mL, which yielded a sensitivity and specificity of 70.4% and 85.7%, respectively. The RR of ESKD progression was significantly higher in those with MPO-ANCA titres ≤ 81.0 IU/mL than in those with MPO-ANCA titres > 81.0 IU/mL (42.9% vs. 5.0%, RR 14.250, 95% CI 1.469, 138.271).

Conclusions

Lower MPO-ANCA titres at diagnosis may be associated with a higher risk of ESKD progression in rituximab-treated MPA patients. These findings suggest that MPO-ANCA titres may be useful in guiding therapeutic decisions for MPA.