LAUSR

To the editor, In the excellent study recently published in the Annals of the Rheumatic Disease ,1 Damoiseaux et al showed a high diagnostic performance of antigen-specific immunoassay for the detection of myeloperoxidase (MPO) and proteinase 3 (PR3) antineutrophil cytoplasmic antibodies (ANCAs). These data challenge the role of indirect immunofluorescence in the ANCA testing algorithm. In our centre, we have discarded ANCA indirect immunofluorescence more than a decade ago. Therefore, new data showing the feasibility of screening by antigen-specific immunoassay have a particular value for us. In the recent series of 284 patients with ANCA-associated vasculitides, we have detected ANCAs by this approach in 96.9% of patients with microscopic polyangiitis (MPA) but only in 72.7% of patients with granulomatosis with polyangiitis (GPA) (table 1). The latter result can be explained by a relatively high occurrence of localised GPA in our series,2 since a rate of ANCA positivity reached 92.2% in patients with renal GPA. View this table: Table 1 Results of ANCA testing in 284 patients with ANCA-associated vasculitis, n (%) ANCA testing should be performed only in the clinical context since PR3-ANCA and MPO-ANCA can be found in the other conditions …