title: Clinical significance of anti-neutrophil cytoplasm antibodies detected by a standardized indirect immunofluorescence assay.
abstract: We assessed the use of a standardized antineutrophil cytoplasm antibody (ANCA) test in diagnosing Wegener's granulomatosis (WG), microscopic polyarteritis (mPA) and systemic vasculitis (SV). All samples (n = 779) tested for ANCA at our laboratory were identified, and clinical information was obtained for 783/779 patients by questionnaire, and by visits where necessary. The combined prevalence of WG/mPA/SV was 123/738 (17%). The ANCA test was positive in 48/68 WG patients (71%; 38 cANCA, 10 pANCA), 22/43 mPA patients (51%; 12 cANCA, 10 pANCA) and 3/12 SV patients (25%). WG and mPA patients in remission had similar frequencies of positive ANCA to those with active disease. The sensitivity and specificity for WG (71% and 80%) and mPA (51% and 80%) were lower than previously reported. In this high-prevalence population, the overall (WG/mPA/SV) positive predictive value was only 40%, and the sensitivity 59%. Only 29% of positive tests were from patients with active disease. Overall, 78% of test results gave a 'true' prediction. On this basis, a diagnosis of necrotizing vasculitis (WG/mPA/SV) can be neither made nor refuted by ANCA test alone.
authors.affiliation: Richard Bright Renal Unit, Southmead Hospital, Bristol, UK.
authors.forename: A
authors.initials: A
authors.lastname: Davenport
authors.forename: R J
authors.initials: RJ
authors.lastname: Lock
authors.forename: T B
authors.initials: TB
authors.lastname: Wallington
authors.forename: T G
authors.initials: TG
authors.lastname: Feest
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019268:Antibodies, Antineutrophil Cytoplasmic; D001167:Arteritis / Q000097:blood / Q000175:diagnosis*; D001323:Autoantibodies / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D005260:Female; D005455:Fluorescent Antibody Technique; D014890:Granulomatosis with Polyangiitis / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D014657:Vasculitis / Q000097:blood / Q000175:diagnosis*
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D001323:Autoantibodies; D015415:Biomarkers; D007074:Immunoglobulin G