Estimating 2-year risk of first relapse in ANCA-associated vasculitis: derivation of a risk-prediction model based on participants in the PEXIVAS trial.

OBJECTIVES

Individuals with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) differ in their risk of relapse. Estimation of an individual's risk may inform decision-making around monitoring and treatment.

METHODS

We performed a post hoc analysis of participants with AAV with an estimated glomerular filtration rate (eGFR) <50 mL/min/1.73 m2 or diffuse alveolar haemorrhage enrolled in a trial assessing the effects of plasma exchange and a reduced glucocorticoid dosing regimen who achieved disease remission. We estimated the risk of first relapse within 2 years of remission. We first identified candidate predictors from the literature. Candidate predictors measured in our data set and associated with relapse within 2 years of remission underwent further selection using least absolute shrinkage and selection operator regression and time-to-event analysis. Model stability was assessed with variable inclusion, multiple shrinkage methods, and VanderWeele's E. Model discrimination was assessed using concordance statistics, and calibration using the slope.

RESULTS

We included data from 649 trial participants, of whom 100 experienced a relapse within 2 years of remission. The final risk estimation model included sex, use of oral cyclophosphamide or rituximab as induction agent, ANCA subtype, nonhaemorrhagic respiratory involvement or mucous membrane/eye involvement at presentation, and eGFR at remission. The optimism-corrected Harrell's area under the receiver-operator curve 0.709 (95% CI 0.707-0.710). The calibration slope was 0.99 (95% CI 0.65-1.34).

CONCLUSIONS

Our model estimates the risk of first relapse for individuals with AAV within 2 years after achieving disease remission. This may inform monitoring and treatment decisions. The model will benefit from future external validation.