Development and performance evaluation of novel chemiluminescence assays for detection of anti-PR3 and anti-MPO antibodies

BackgroundThe detection of anti-proteinase 3 (PR3) and anti-myeloperoxidase (MPO) autoantibodies represents a serological hallmark in the diagnosis of small vessel vasculitis such as granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). We evaluated novel chemiluminescence assays (CIAs) for PR3- and MPO-ANCA detection and investigated their utility for disease activity monitoring.MethodsSera collected from GPA (n = 41) and MPA (n = 30) patients were tested by QUANTA Lite® PR-3 and MPO ELISAs (INOVA Diagnostics) and by the QUANTA Flash™ PR3 and MPO CIAs (INOVA). Precision and linearity were analyzed following reference guidelines. The recently launched reference sera for PR3-and MPO-ANCA (Centers of Disease Control and prevention, CDC) were used to establish international units for the new assays. Disease activity was determined using the Birmingham Vasculitis Activity Score.ResultsThe international standards for PR3-and MPO-ANCA yielded results of 403 CU and 332 CU in the novel CIAs, respectively. The linearity analysis showed linear regression values > 0.97 with slopes between 0.96 and 1.04. Total variation obtained from the precision study showed CV% of ≤ 7.4 for PR3-ANCA and ≤ 12.8 for MPO-ANCA. Good agreement (Spearman rho ≥ 0.89) was observed between CIA and ELISA. PR3-ANCA determined by CIA, but not by ELISA, was correlated with disease activity. No correlation was found for MPO-ANCA.ConclusionThe novel PR3- and MPO-ANCA CIAs show good precision, linearity and correlation to ELISA. In addition, PR3-ANCA by CIA show correlation with disease activity.