ELISA is the superior method for detecting antineutrophil cytoplasmic antibodies in the diagnosis of systemic necrotising vasculitis.
BACKGROUND
Antineutrophil cytoplasmic antibodies (ANCA) have been used as a diagnostic marker for systemic necrotising vasculitis, a disease classification which includes Wegener granulomatosis, microscopic and classic polyarteritis nodosa, and Churg Strauss disease.


OBJECTIVE
To compare the diagnostic value of the two methods for detecting these antibodies--immunofluorescence and enzyme linked immunosorbent assay (ELISA)--with respect to biopsy proven active systemic necrotising vasculitis in a clinically relevant population.


METHODS
A prospective study to ascertain the patient's diagnosis at the time of each of the 466 requests for ANCA received at one laboratory over a nine month period, and allocate each to one of five diagnostic groups: active and inactive biopsy proven systemic necrotising vasculitis, suspected systemic necrotising vasculitis, low probability systemic necrotising vasculitis, and not systemic necrotising vasculitis.


RESULTS
ELISA was superior to immunofluorescence in the diagnosis of systemic necrotising vasculitis because it was less likely to detect other diseases. This was reflected in its specificity of 97% and positive predictive value of 73%, compared with 90% and only 50% for immunofluorescence (p = 0.0006 and p = 0.013, respectively). ELISA had a negative predictive value of 98% which was not significantly different to immunofluorescence. ELISA was technically superior.


CONCLUSIONS
ELISA is the superior method of ANCA detection in the diagnosis of systemic necrotising vasculitis and should be used in conjunction with a compatible clinical picture and histological evidence.
Harris
A
A
Institute of Medical and Veterinary Science, Adelaide, South Australia. a.harris5@pgrag.unimelb.edu.au
Chang
G
G
Vadas
M
M
Gillis
D
D
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000032:analysis*; D015415:Biomarkers / Q000032:analysis; D002648:Child; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D014657:Vasculitis / Q000175:diagnosis*
D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers