Background: Both antineutrophil cytoplasmic antibodies and proteinase 3 (PR3) are high-risk stratified autoantibodies 1 often seen in patients with granulomatosis with polyangiitis (GPA). 2 In the RCPAQAP vasculitis antibodies external quality assurance program, both Bio-Rad BioPlex (multiplex flow immunoassay) and the recently enrolled YHLO (chemiluminescence immunoassay) methods have returned potential false-negative PR3 interpretations from two confirmed GPA patients over a 3-year period. We sought to investigate this discrepancy.
Fernandez et al. (Sun,) studied this question.