The ANCA assay (INOVA) detects the presence of IgG antibodies that bind to human neutrophil antigens using direct immunofluorescence.¹,² Screening all samples with ethanol fixed slides allows ANCA reactivity to be separated into two diagnostically useful categories. The pattern and semiquantitative titer are reported. Current research indicates that two patterns may be clinically useful:
- A granular cytoplasmic pattern (cANCA) is a serologic marker in up to 96% of Wegener’s granulomatosis patients. This severe systemic vascular disease that causes irreversible injury to the kidneys and lungs presents with initial symptoms and biopsy findings that are frequently non-specific. Early diagnosis and treatment can greatly improve renal outcome. The degree of reactivity of cANCA has been found to follow the disease course so repeat testing can be important in disease management. The antigenic specificity of this pattern is primarily serine protease 3 (PR3).
- A classic perinuclear pattern (pANCA) is primarily due to antibodies to myeloperoxidase (MPO) but may also be caused by others including elastase and lactoferrin. This pattern has been associated with more organ-limited vasculitis, in particular rapidly progressive glomerulonephritis. All pANCA reactions on ETOH-fixed slides are confirmed by testing on formalin slides.
ANCA antibodies have been associated with ulcerative colitis² and primary sclerosing cholangitis but the specific antigen is unknown at this time.
Reactivity to other cytoplasmic and nuclear antigens may be observed. Concurrent antinuclear antibody (ANA) screening with Hep-2 cells may aid in determining the specificity of the antibodies.
References
1. Maduskuie, V.L., Budd, S.M., Fawcett, P.T., “Comparison of Immunofluorescence and ELISA for Detection of ANCA in a Pediatric Setting,” American College of Rheumatology 68th Annual Scientific Meeting, San Antonio, TX. November, 2004.
2. Proujansky, R., Fawcett, P.T., Gibney, K.M., Treem, W.R. and Hyams, J.S. Examination of anti-neutrophil cytoplasmic antibodies in childhood inflammatory bowel disease. J. Ped. Gastroenterology and Nutrition 17:193-197, 1993.