Evaluation of the diagnostic performance of an immunoblot for ANCA and anti-GBM antibody detection

Abstract

The use of high-quality antigen-specific immunoassays for detecting anti-neutrophil cytoplasmic antibodies (ANCA) and anti-glomerular basement membrane (GBM) autoantibodies is recommended in patients with suspected ANCA vasculitis and/or anti-GBM disease. We analysed the diagnostic performance of a semi-quantitative and rapid immunoblot (EUROIMMUN AG, Lübeck, Germany) in two settings. Patient sera from different cohorts (ANCA vasculitis n = 187, anti-GBM disease n = 19, and disease controls n = 51) were used. The diagnostic performance of the immunoblot was assessed when used as a confirmatory test for the presence of ANCA in suspected ANCA vasculitis and when evaluating the presence of ANCA and/or anti-GBM antibodies in AAV and/or anti-GBM disease patients with a rapidly progressive glomerulonephritis (RPGN). In a confirmatory test setting, the immunoblot had an optimal sensitivity and specificity of 97.4 and 98.1% for PR3-ANCA and 98.5 and 96.4% for MPO-ANCA, respectively. With increasing test result ranges, a higher interval likelihood ratio (LR) was found for both ANCA entities. When evaluating for ANCA in patients with RPGN, the highest diagnostic accuracy (sensitivity 92.9% and specificity 100%) was obtained by using different cut-off values of positivity for PR3- (>5) and MPO-ANCA (>10). Also, the diagnostic performance for detecting anti-GBM was good (sensitivity 100% and specificity 100%). There are advantages over other assays in terms of time, costs, and interpretation of results. The immunoblot is a useful addition to current guidelines, particularly when a rapid diagnosis is necessary.

Keywords:

• Anti-neutrophil cytoplasmic antibodies (ANCA)
• glomerular basement membrane (GBM)
• autoantibodies
• serology
• AKI
• diagnostics

Acknowledgements

Euroimmun AG (Lübeck, Germany) and Biognost (Wevelgem, Belgium) are acknowledged for providing reagents free of charge.

Author contributions

M.H.B. and J.G.M.C.D. designed the study, carried out the experiments, and analysed the data. M.H.B., J.P.A., J.J.B.C.B., P.P., and J.G.M.C.D. drafted the paper; all authors approved the final version of the manuscript.

Disclosure statement

The authors report no conflicts of interest.

Additional information

Funding

No funding was obtained for this study.