CLINICAL-EVALUATION OF A CAPTURE ELISA FOR DETECTION OF PROTEINASE-3 ANTINEUTROPHIL CYTOPLASMIC ANTIBODY - TECHNICAL NOTE

Detection of antineutrophil cytoplasmic antibodies (ANCA) has become a useful tool in the diagnosis of Wegener's granulomatosis and microsco pic polyangiitis. However, the results obtained with indirect immunofl uorescence (IIF) and by ELISA for ANCA demonstration do not always cor relate. A possible explanation for this finding could be that proteins are denatured during the process of antigen purification or during co ating onto the solid phase. To avoid this possibility, a monoclonal an tibody to PR3 that is precoated on the plate can be used. In the prese nt study we have used the monoclonal antibody (MoAb) 4A3 for the captu re of PR3 in an ELISA, and a clinical evaluation of the diagnostic pro perties of the new capture ELISA has been made. The sensitivity of the capture PR3-ANCA ELISA was 85% in a material of c-ANCA positive sera. A specificity of 90% ws obtained in analyses from patients having var ious forms of glomerulonephritis. There was a significantly higher dia gnostic sensitivity of the capture PR3-ANCA ELISA (85%) compared to c- ANCA by IIF (58%) in patients with Wegener's granulomatosis with renal involvement. Capture PR3-ANCA and direct ELISA for MPO-ANCA together gave a diagnostic sensitivity of 98%, versus 75% using IIF. In conclus ion, the capture PR3-ANCA ELISA seems to be a valuable tool in the dia gnosis of Wegener's granulomatosis with renal involvement. Preliminary data suggest that the technique may have an advantage over direct ELI SA for PR3-ANCA, as well as in the follow-up of c-/PR3-ANCA associated vasculitides. However, further prospective studies are needed to clar ity this premise.