To save this page as a PDF, click this button and choose the PDF destination.

80

Performance Evaluation of BioPlex 2200 Vaculitis test and Comparison with ELISA for ANCA and anti-GBM Antibody Screening

Song Lu1,2, Robin Laskowski1, Aimee Roewekamp1, Simone Corriveau1, Fang Wu1,2
1Saskatchewan Health Authority, Saskatoon, Saskatchewan, Canada. 2University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Abstract

Objective

The anti-neutrophil cytoplasmic antibodies (anti-MPO and -PR3) and anti-GBM play a crucial role in the diagnosis of autoimmune vasculitis. The BioPlex 2200 Vasculitis panel is a semi-quantitative multiplex bead assay that simultaneously detects ANCA and anti-GBM antibody. In this study, we evaluated the analytical performance of this test as a primary screening method.

Methods

Manufacturer-claimed performance parameters were verified per CLSI guidelines for FDA-approved methods. A calibrator set was used to verify linearity. On-board dilution factors were verified by serial dilution of pooled patient samples. In addition to quantitative comparison, we compared the BioPlex assay and ELISA (Euroimmun) or IFA results qualitatively. The total allowable error was selected as ±30% based on literature and CAP survey.

Results

The total CV% of ANCA was < 5%. Between-day CV% of anti-GBM was slightly higher but < 10%. All 3 assays demonstrated linearity (slope: 0.966 to 1.02, intercept: -0.13 to 0.02) across manufacturer-claimed AMR (0.2-8.0 AI). However, the linearity was not retained after dilution due to elevated recovery (> 110%). The BioPlex method run in the local lab and reference lab were comparable quantitatively (slope: 0.989 to 1.010, intercept: -0.39 to 0.53, R: 0.984 to 0.999). In the qualitative comparison, ANCA was highly consistent between BioPlex and ELISA (Kappa: 0.789 to 0.943). Although BioPlex detected fewer anti-GBM positive samples than ELISA, it correlated well with the gold standard IFA (sensitivity: 100%, specificity: 80%). Finally, all 3 autoantibodies were below manufacturer-claimed cutoff (0.2 AI) in 30 healthy donor samples.

Conclusions

The BioPlex 2200 vasculitis panel meets the manufacturer-claimed performance goals. The qualitative interpretation of BioPlex result is consistent with ELISA for ANCA tests, whereas BioPlex correlates well with IFA for anti-GBM except some false positive cases. With IFA confirmation of positive results, BioPlex 2200 vasculitis panel can serve as a primary screening method for autoimmune vascuiltis.