A novel enzyme-linked immunosorbent assay using a mixture of human native and recombinant proteinase-3 significantly improves the diagnostic potential for antineutrophil cytoplasmic antibody-associated vasculitis.
BACKGROUND
Antineutrophil cytoplasmic antibodies (ANCA) with a C-ANCA or P-ANCA pattern are detected in ANCA-associated vasculitis (AAV). While in most patients with AAV a C-ANCA pattern is due to reactivity with proteinase-3 (PR3)-ANCA, some C-ANCA-positive sera do not react with PR3.


OBJECTIVE
The development and evaluation of a direct enzyme-linked immunosorbent assay (ELISA) for PR3-ANCA with increased sensitivity.


METHODS
A mixture of human native (hn) and human recombinant (hr) PR3 was used as antigen coating. The resulting ELISA (anti-PR3-hn-hr) was compared with ELISAs using directly coated hn-PR3 or hr-PR3, as well as with a hn-PR3 capture ELISA. Assay characteristics were determined in patients with AAV (n = 248), with special attention for those patients with C-ANCA (n = 132), as well as disease controls (n = 585) and healthy controls (n = 429). Additionally, for prediction of relapses serial samples of 46 patients with PR3-AAV were analysed.


RESULTS
At a predefined specificity of 99% both ELISAs containing hr-PR3 revealed a substantial increase in sensitivity. For the prediction of relapses by rises in PR3-ANCA titres the capture ELISA was most optimal (odds ratio 12.5). With an odds ratio of 8.9 the novel anti-PR3-hn-hr ELISA was second best.


CONCLUSIONS
Owing to the very high sensitivity of the novel anti-PR3-hn-hr ELISA for the detection of PR3-ANCA in C-ANCA-positive samples of patients with AAV this assay has an excellent diagnostic performance. This feature is combined with a good predictability of clinical relapses in patients with PR3-AAV. These characteristics challenge the dogma that, for detection of PR3-ANCA, capture ELISAs are superior for diagnosis and follow-up.
Damoiseaux
J
J
Department of Clinical and Experimental Immunology, University Hospital Maastricht, PO Box 5800, 6202 AZ Maastricht, The Netherlands. jan.damoiseaux@mumc.nl
Dähnrich
C
C
Rosemann
A
A
Probst
C
C
Komorowski
L
L
Stegeman
C A
CA
Egerer
K
K
Hiepe
F
F
van Paassen
P
P
Stöcker
W
W
Schlumberger
W
W
Tervaert
J W Cohen
JW
D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood*; D001327:Autoimmune Diseases / Q000175:diagnosis* / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006801:Humans; D053146:Myeloblastin / Q000276:immunology*; D011379:Prognosis; D011994:Recombinant Proteins / Q000276:immunology; D012008:Recurrence; D012680:Sensitivity and Specificity; D014657:Vasculitis / Q000175:diagnosis* / Q000276:immunology
D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers; D011994:Recombinant Proteins; D053146:Myeloblastin