|Downtime form:||A-1a Doctor/Provider Orders - Pathology Immunopathology|
Pediatric - 2 mL; red top tube
Test includes both C-ANCA and P-ANCA screening and titering. MPO and PR3 confirmatory tests are performed if screen is positive or inconclusive. Anti-neutrophil cytoplasmic antibodies are associated primarily with two groups of diseases: systemic necrotizing vasculitis/glomerulonephritis and inflammatory bowel and liver disease.
Because the laboratory testing strategies are different for these two groups of disease, different tests must be ordered for each of these workups. "ANCA" is the test to be ordered when vasculitis/ glomerulonephritis is in the differential diagnosis. "UC-ANCA" is the test to order to evaluate patients with suspected inflammatory bowel or liver disease (see UC-ANCA listing for more testing information).
The "ANCA" test starts with immunofluorescence screening for both C-ANCA (primarily associated with Wegner's granulomatosis) and p-ANCA (primarily associated with microscopic polyarteritis and pauci-immune GN). If the ANCA screen is positive, titration to end-point is performed. It is strongly recommended that confirmatory testing for anti-proteinase 3 (PR3) and anti-myeloperoxidase (MPO) be performed at the time of initial identification of ANCA. P-ANCA can be confused with "UC-ANCA" or ANA on IFA screening. Approximately 5% of patients with either "C-ANCA" or "P-ANCA" will have a specificity different from that usually associated with the ANCA IFA pattern (eg: P-ANCA may have PR3 specificity and the C-ANCA may have MPO specificity).
MPO and PR3: Multiplex flow immunoassay