Page 179 - The Vasculitides, Volume 1: General Considerations and Systemic Vasculitis

Detection Techniques and Clinical Relevance of ANCA Testing … 155

However the sensitivity of capture ELISA may also be reduced by capturing antibodies
which can hide relevant epitopes.

AB

C

Figure 1. ANCA immunofluorescence patterns on ethanol-fixed neutrophils. A) C-ANCA; B) P-
ANCA; and C) A-ANCA.

The anchor PR3-ANCA ELISA methodology immobilizes PR3 via a bridging molecule
to the plastic plate preserving all epitopes for ANCA binding, and thus demonstrates
superiority to direct and capture ELISA assays [6, 7]. A novel generation of ANCA ELISA
has only recently become available and is currently undergoing evaluation. An analysis of the
diagnostic performance of 11 commercial PR3- and MPO-ANCA ELISA among them direct,
capture and anchor ELISA systems, in the identification of subjects with AAV that compared
the binding of PR3- and MPO-ANCA in international standards when tested at dilutions
recommended by the manufactures [8] found that all were highly sensitive and specific for
active vasculitis and are able to differentiate active vasculitis from other diseases. Maximum
sensitivity for ANCA was obtained with IFT and ELISA in GPA and MPA employing both
capture and anchor for PR3-ANCA, and capture and direct for MPO-ANCA) [8].

The emergence of new detection technologies, automated platforms, and laboratory
environments has led to updating of the standardization process and a revision of existing

Complimentary Contributor Copy