Traditionally, laboratory tests of myeloperoxidase (MPO) and proteinase 3 (PR3)-ANCAs are useful biomarkers for the diagnosis and assessment of prognosis in the context of MPA/GPA6, but also with limitations that its titres alone are not sufficient to confirm diagnosis or monitor therapeutic response during follow‐up of patients7. This evidence concerns the gene PRTN3 and microscopic polyangiitis.