Do ANCA titers fluctuate with disease activity?
This is controversial. There is some evidence among patients with granulomatosis with polyangiitis (who are PR3-positive), especially those treated with rituximab, that rising titers of C-ANCA or PR3 can correlate with disease activity. In addition, in patients treated with rituximab who subsequently become C-ANCA/PR3-negative, absence of antibody coupled with undetectable peripheral B-cell counts is associated with a low risk of flare. However, patients with stable or negative ANCA titers have been known to flare, while those with rising titers may not, indicating that changes in ANCA titers need to be coupled with clinical assessment to inform decisions on subsequent therapy. There is little evidence that P-ANCA titers fluctuate with disease activity.