PEXIVAS model estimates two-year relapse risk after remission in severe ANCA vasculitis

Design

Post hoc prediction-model derivation from a randomised trial (PEXIVAS)

Population

649 patients with ANCA vasculitis in remission (eGFR <50 or alveolar haemorrhage at entry)

Primary outcome

First relapse within 2 years of remission

Effect

C-statistic 0.71; calibration slope 0.99 (0.65 to 1.34); 100 relapses

This post hoc analysis used 649 PEXIVAS participants — all with eGFR below 50 or diffuse alveolar haemorrhage — who reached remission; 100 relapsed within two years.

The final model used sex, induction agent (oral cyclophosphamide or rituximab), ANCA subtype, non-haemorrhagic respiratory or mucosal and eye involvement at presentation, and eGFR at remission. Optimism-corrected discrimination was 0.71, and calibration was good (slope 0.99).

A discrimination of 0.71 is moderate: useful for grouping patients, less so for a single individual. The model is not externally validated, and it applies only to the severe, renal or haemorrhagic population PEXIVAS enrolled.

• Record the model's variables at remission: ANCA type, induction agent, eGFR, organ involvement.
• Use relapse risk to inform how closely to monitor, not yet how long to maintain.
• Remember PR3-ANCA and respiratory involvement carry higher relapse risk.
• Wait for external validation before using it to stop maintenance.

Why it matters

It turns familiar risk factors into a single estimate that can guide follow-up.

Don't overread it

Derived from trial participants with severe disease and not externally validated.

The statistics, in plain English

A C-statistic of 0.71 means the model ranks a relapsing patient above a non-relapsing one about 71% of the time. A calibration slope near 1 means predicted and observed risks agree on average.

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