Is there a role for monitoring serum ANCAs to assess ANCA associated vasculitis disease activity?

This is (and remains) a somewhat controversial question. ANCA titers do appear to rise in anticipation of disease flares and patients with persistent titers appear to have more flares. This is especially true for PR3 ANCAs. However, the proximity of flares to rising ANCA titers is not terribly close...

Every visit.

Each visit, it is a marker to predict disease flare and need to resume rituximab or increase therapy.