Brouwer et al. (10) further demonstrated both in vitro and in vivo that the numbers of activated neutrophils within kidney biopsies of patients with Wegener's granulomatosis correlated significantly with serum creatinine levels taken at the time of biopsy (22 PR3 positive and 5 MPO positive) (10). This evidence concerns the gene PRTN3 and granulomatosis with polyangiitis.