Rituximab maintenance in ANCA vasculitis: risk scores for relapse and infection held up in MAINRITSAN

Design

External validation of prediction models in long-term trial follow-up

Population

217 patients with ANCA-associated vasculitis on rituximab maintenance (MAINRITSAN 1 and 2)

Primary outcome

Relapse-free and serious infection-free survival

Effect

Infection model HR 2.93 (1.28–6.72); relapse model HR 1.91 (0.97–3.76)

Long-term follow-up of the MAINRITSAN trials established rituximab as maintenance therapy in ANCA-associated vasculitis, but how long to continue beyond 18 months is unsettled. A French analysis applied two previously published prediction models to 217 trial patients followed for up to six years.

Relapse occurred in 76 patients; 55% were relapse-free at 72 months. The relapse model — male sex, age over 60, ANCA positivity, relapsing disease, ENT involvement and prednisone dose — predicted major relapse, mainly in PR3-ANCA disease, though separation between high- and low-risk groups was borderline. Serious infections affected 33 patients, with a 20% cumulative incidence at 72 months. The infection model — male sex, structural lung disease, diabetes, infections during maintenance and gammaglobulin level — separated risk more clearly, with nearly three times the hazard in the high-risk group.

Used together, the scores give a framework for the extension conversation: a PR3-positive patient with ENT disease and few infection risks may benefit from longer rituximab, while one with low IgG, lung disease and diabetes may be harmed by it.

• Assess relapse risk factors — PR3-ANCA, ENT involvement, prior relapse, persistent ANCA, age over 60 — when deciding on rituximab beyond 18 months.
• Assess infection risk factors — low IgG, structural lung disease, diabetes, infections on maintenance — at the same review.
• Check immunoglobulin levels before each rituximab course during maintenance.
• Discuss both risks with the patient; the infection model predicted more strongly than the relapse model.
• Consider infection prophylaxis and vaccination in patients continuing rituximab with high infection risk.

Why it matters

It turns an often intuitive decision into one that can be discussed with numbers, particularly for PR3-ANCA patients.

Don't overread it

The relapse model only borderline separated risk groups overall; these scores support discussion rather than dictate duration.

The statistics, in plain English

A hazard ratio of 2.93 (95% CI 1.28 to 6.72) for serious infection means high-risk patients had about three times the rate. The relapse model's hazard ratio of 1.91 had an interval crossing 1.0 (0.97 to 3.76), so its separation was less certain.

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