Antineutrophil cytoplasmic antibodies (ANCAs) are autoantibodies that mistakenly attack proteins within neutrophils. ANCAs that target the proteins myeloperoxidase (MPO) and proteinase 3 (PR3) are the most common. There are two types of ANCA tests that are distinguished by different immunofluorescent staining patterns using human neutrophil substrates:
Cytoplasmic ANCAs (cANCAs) produce a diffuse cytoplasmic staining of neutrophils and monocytes and are specific for PR3. cANCA is found in the sera of patients with Wegener granulomatosis (WG).
Perinuclear ANCAs (pANCAs) produce a perinuclear staining of neutrophils and are specific for other neutrophil enzymes, including MPO, elastase, and lactoferrin. pANCA specific for MPO is found in the sera of patients with systemic vasculitis, most of whom have kidney involvement characterized by pauci-immune necrotizing glomerulonephritis.
Negative for ANCAs by IFA
If positive for cANCA, results are titered.
If positive for pANCA, MPO testing is performed by ELISA. Not all specimens positive for pANCA are MPO positive.
Collect a 7-mL blood serum sample in a red-topped tube. Observe standard precautions.
Label the specimen with the patient’s name, date, and test(s) ordered and place in a biohazard bag for transport to the laboratory.
In patients with active generalized WG (pulmonary or kidney involvement), the frequency of positive cANCA results approaches 85%. A negative test for cANCA does not rule out WG; however, false-positive results are rare.
In patients with known WG, rising titers of cANCA suggest relapse, and falling titers suggest successful treatment.
In patients with active kidney disease, a positive pANCA suggests the presence of antibodies to MPO and pauci-immune necrotizing glomerulonephritis.
Results of tests for ANCA should be considered along with other clinical, laboratory, and histopathologic data in establishing the diagnosis of WG or systemic vasculitis.
Inflammatory bowel disease–associated ANCAs are found in ulcerative colitis and Crohn disease, specifically pANCA.
Pretest Patient Care
Explain test purpose and procedure.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan if needed based on the test results in light of the patient’s history, including other clinical, laboratory, and histopathologic data. Positive ANCA results (pANCA and, rarely, cANCA) may occur in patients with diseases other than WG or vasculitis, including Goodpasture syndrome and SLE.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.