title: Clinical significance of antiproteinase 3 antibody positivity in cANCA-positive patients.
abstract: We addressed the clinical significance of antiproteinase 3 (anti-PR3) antibody (Ab) positivity by reviewing the files of 79 patients whose serum contained antineutrophil cytoplasmic antibodies with a cytoplasmic staining pattern (cANCA) and had been tested for anti-PR3 reactivity. Vasculitis was present in most (22/35) cANCA+ PR3+ patients but in only a few (5/44) cANCA+ PR3- patients, thereby suggesting that anti-PR3 Ab positivity in cANCA+ patients is more indicative of vasculitis than cANCA positivity alone. Noteworthy, one-third of cANCA+ PR3+ patients -- those with anti-PR3 Ab titres lower than 100 U/ml -- did not suffer from vasculitis. Anti-PR3 reactivity in vasculitis patients was only weakly associated with Wegener's granulomatosis (WG), as nine out of 22 cANCA+ PR3+ vasculitis patients (41%) did not fulfil the ACR classification criteria for WG. There was no correlation between anti-PR3 Ab titres and disease activity at diagnosis. However, titres measured when patients were in remission were much lower than initial values. Taken together, our results indicate that anti-PR3 Ab positivity should be interpreted in its clinical context.
authors.affiliation: Department of Rheumatology, Cliniques Universitaires Saint-Luc, Louvain Medical School, Brussels, Belgium.
authors.forename: V
authors.initials: V
authors.lastname: van Pesch
authors.forename: M
authors.initials: M
authors.lastname: Jadoul
authors.forename: C
authors.initials: C
authors.lastname: Lefèbvre
authors.forename: B R
authors.initials: BR
authors.lastname: Lauwerys
authors.forename: J P
authors.initials: JP
authors.lastname: Tomasi
authors.forename: J P
authors.initials: JP
authors.lastname: Devogelaer
authors.forename: F A
authors.initials: FA
authors.lastname: Houssiau
mesh_terms: D019268:Antibodies, Antineutrophil Cytoplasmic / Q000276:immunology*; D001323:Autoantibodies / Q000032:analysis*; D001324:Autoantigens / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay; D014890:Granulomatosis with Polyangiitis / Q000097:blood / Q000175:diagnosis / Q000276:immunology*; D006801:Humans; D053146:Myeloblastin; D012189:Retrospective Studies; D012697:Serine Endopeptidases / Q000276:immunology*; D012720:Severity of Illness Index
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D001323:Autoantibodies; D001324:Autoantigens; D015415:Biomarkers; D012697:Serine Endopeptidases; D053146:Myeloblastin