Evaluation of the FIDIS Vasculitis Multiplex Immunoassay for Diagnosis and Follow‐up of ANCA‐Associated Vasculitis and Goodpasture's Disease

Authors:
  • MVM. Vaessen
    M. Vaessen
  • YKY. Knapen
    Y. Knapen
  • ECE. Csernok
    E. Csernok
  • CSC. A. Stegeman
    C. A. Stegeman
  • PPP. VAN Paassen
    P. VAN Paassen
  • JTJ. W. Cohen Tervaert
    J. W. Cohen Tervaert
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Abstract
We have evaluated a new‐multiplex immunoassay (FIDIS Vasculitis) for simultaneous detection and quantification of anti‐MPO, ‐PR3, and ‐glomerular basement membrane (GBM) antibodies in diagnosis and follow‐up of ANCA‐associated vasculitides (AAV) and Goodpasture's disease. ANCA were determined in sera of (a) 87 consecutive patients with biopsy‐proven pauci‐immune NCGN and 72 controls; (b) 9 patients with Goodpasture's disease; and (c) 60 WG patients and 60 controls, previously used in a multicenter comparison of direct and capture ELISA for PR3‐ANCA. Finally, for prediction of relapses, PR3‐ANCA was measured in samples preceding relapse in 23 PR3‐AAV patients and in 23 matched PR3‐AAV patients without relapse. The relative sensitivity of the FIDIS Vasculitis assay was 97.4% for MPO‐ANCA and 92.3% for PR3‐ANCA; specificity was 100% and 97.2%, respectively. Evaluation of the anti‐GBM antibody detection revealed a sensitivity of 100% and a specificity of 99.6%. The sensitivity for WG of the PR3‐ANCA detection (71.6%) approached the performance of capture ELISA (74%), although at the cost of specificity (96.7% versus 100%). For prediction of relapses a rise of 50% in ANCA level by FIDIS Vasculitis appeared optimal (ROC curve) for prediction of relapses. However, as compared to capture ELISA, both positive (63% versus 76%) and negative (68% versus 72%) predictive values were reduced. In conclusion, simultaneous detection of anti‐MPO, ‐PR3, and ‐GBM antibodies in the multiplex FIDIS Vasculitis assay has excellent performance in terms of diagnosis of patients with AAV or Goodpasture's disease. However, detection of rises in PR3‐ANCA for prediction of relapses gives less optimal results when compared to capture ELISA.

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