The measurement of c-ANCA and p-ANCA antibodies is used in the laboratory diagnosis of granulomatous vascular diseases, such as Wegener's granulomatosis and microscopic polyangiitis, as well as in monitoring the progression of the disease, monitoring the response to treatment, and in the timely detection of its recurrences.
The ANCA antibodies (AntiNeutrophil Cytoplasmic Antibody) are directed against the cytoplasmic components of neutrophil granulocytes. Wegener's granulomatosis is a peripheral systemic vasculitis in which the small arteries of the kidneys, lungs, and upper respiratory tract (nasopharynx) suffer damage from the development of granulomatous inflammation. The diagnosis is confirmed by a biopsy of the tissue presenting the clinical symptoms. Serological tests play a key role in the diagnosis of Wegener's granulomatosis and other systemic vasculitis syndromes.
When ANCA antibodies are detected by indirect immunofluorescence microscopy, two major patterns of staining are observed: cytoplasmic ANCA (c-ANCA) and perinuclear ANCA (p-ANCA). Specific immunochemical methodologies demonstrate that c-ANCA mainly consists of antibodies against proteinase 3 (PR3) and p-ANCA consists of antibodies against myeloperoxidase (MPO).
Autoantibodies against proteinase 3 antigen (PR3) are highly specific (95-99%) for Wegener's granulomatosis. When the disease is limited to the respiratory tract, antibodies against PR3 are positive in 65% of patients. Almost all patients with renal limited Wegener's granulomatosis do not have positive PR3 antibodies. When Wegener's granulomatosis is inactive, the percentage of positive PR3 antibodies drops to 30%.
Autoantibodies against myeloperoxidase antigen (MPO) are found in 50% of patients with renal limited Wegener granulomatosis. It also occurs in patients with other causes of glomerulonephritis (other than Wegener's granulomatosis), such as microscopic polyangiitis (MPA).
The p-ANCA antibodies can also be used to differentiate inflammatory bowel diseases. P-ANCA antibodies were found in 50-70% of patients with ulcerative colitis (UC), but only in 20% of patients with Crohn's disease (CD).
What Do Pathological Values Mean?
- Increase: Wegener granulomatosis, microscopic polyarthritis, idiopathic rapidly evolving glomerulonephritis, ulcerative colitis, primary sclerosing cholangitis, autoimmune hepatitis, Churg-Strauss vasculitis, active viral hepatitis, Crohn's disease.
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
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