Antineutrophil cytoplasmic antibody (ANCA), Wegener’s Granulomatosis
- The patient serum is needed.
- How to get good serum: Take 3 to 5 ml of blood in the disposable syringe or in vacutainer. Keep the syringe for 15 to 30 minutes at 37 °C and then centrifuge for 2 to 4 minutes to get the clear serum.
- No special precaution required.
- Separate serum as soon as possible and freeze it.
- Slides from the blood are made and perform the indirect immunofluorescent technique for the neutrophils.
- Two types of staining patterns seen for two different antibodies.
Purpose of the test (Indications)
- For the diagnosis of Wegener’s granulomatosis.
- This is also done to follow the course of the disease and monitor the response to treatment of Wegener’s granulomatosis.
- This may be done for other autoimmune diseases.
- This test is indicated in the case of vasculitis and in inflammatory bowel disease.
- This is also called an anti-cytoplasmic antibody. These are formed against the antigen in the cytoplasm of the neutrophils and also of the monocytes.
- The majority of these are IgG type.
- There is regional vasculitis involving the small arteries of kidneys, lungs, and upper respiratory tract.
- The pathologic damage is by the granulomatous inflammation.
- These are autoantibodies against the myeloid-specific lysosomal enzyme.
- ANCA is seen in autoimmune diseases with vasculitis e.g. Necrotising vasculitis, active Wegener’s granulomatosis, Polyarteritis nodosa, and in renal failure.
- These are 85 to 100 % positive in Wegener’s granulomatosis.
Types of ANCA
- When patient sera are incubated with alcohol-fixed neutrophils, indirect immunofluorescence shows two patterns:
- c-ANCA (cytoplasmic ANCA) is highly specific 95 to 99% of Wegener’s granulomatosis and there is diffuse granular staining of the cytoplasm of neutrophils and monocytes (by fluorescent antibody technique ).
- In respiratory disease, it is present in only about 65 % of the cases.
- All Wegner’s patients with limited disease in the kidney are not positive for c-ANCA.
- When Wegner’s is not active then % drops to 30%.
- A negative result for c-ANCA does not rule out Wegener’s.
- False-positive results are rare.
- Rising titer for c-ANCA suggests relapse.
- When titer is falling indicates successful treatment.
- p-ANCA (perinuclear ANCA) produces a perinuclear pattern of staining in the neutrophils cytoplasm.
- It is found in about 50% of the patient with kidney disease.
- This is also positive (about 75%) in other autoimmune diseases like Ulcerative colitis or sclerosing cholangitis.
- c-ANCA appears to have anti-proteinase 3 specificity, while p-ANCA has predominantly anti-myeloperoxidase activity.
- Result: Negative when there is very little fluorescence or no fluorescence.
- There is regional systemic vasculitis or fatal granulomatous vasculitis.
- Small arteries of the kidneys, lungs, and upper respiratory system (nasopharynx) are involved.
- The damage is due to granulomatous inflammation.
- The renal lesion is focal segmental necrotizing glomerulonephritis.
- It is a form of vasculitis which involves small and medium-sized blood vessels in various organs.
- The common sites are the kidneys and respiratory system.
- Diagnostic criteria:
- Necrotizing granulomas in the respiratory tract.
- Generalized necrotizing arteritis.
- Signs and symptoms are:
- The patient has fever and arthralgia.
- Nose bleed, epistaxis.
- Stuffy nose, nasal ulceration, and crusty secretions.
- Rhinitis is the first symptom.
- There is sinus involvement.
- Ear shows conductive hear loss due to auditory dysfunction.
- There are otitis media.
- The kidney shows glomerulitis.
- There is hypertension.
- The oral cavity shows nonspecific mucosal ulceration.
- There is gingivitis.
- Bone destruction and loosening of the teeth.
- Lung shows pulmonary nodules like coin lesions.
- There is infiltrate looking like pneumonia.
- There is pulmonary hemorrhage leading to hemoptysis.
- Rarely there is bronchial stenosis.
- The skin may show a subcutaneous nodule which is like granuloma.
- There may cutaneous vasculitis.
- CNS may show sensory neuropathy.
- Multiple cranial nerve involvement.
- The eye shows Inflammation like:
- scleritis and conjunctivitis are common.
- There is proptosis or ptosis.
- There are orbital granulomas.
- There is a corneal ulcer.
- There may scleritis or episcleritis.
- There may be uveitis.
- There may be retinitis.
- Damage to the heart, lungs, and kidneys may be very severe.
- Usually, heart, CNS, and GI tract involvement is rare.
- Histologically there are poorly formed granulomas, with the presence of necrosis and many multinucleated giant cells.
- It is believed that ANCA antibodies are responsible for the inflammation.
- Serological method for the detection of ANCA.
- Detection of c-ANCA is sensitive and specific for the diagnosis of Wegener’s disease.
- A biopsy is more diagnostic.
- Serological method
- Not found normally in the serum.
- Negative = <1:20
- Not found normally in the serum.
- ANCA by EIA =
- Negtive = <21 units
- Weak positive = 21 to 30 units
- Positive = >30 units.
- Tissue biopsy
- Negative for ANCA by IFA.
- In positive c-ANCA, then the results are titrated.
- In positive p-ACNA, MPO (myeloperoxidase) testing is performed by ELIZA.
- Not all p-ANCA cases are positive for MPO.
- Blood = Negative
- ANCA is also found in ulcerative colitis and inflammatory bowel disease.
- Also positive in Crohn’s disease specifically p-ANCA.
- Wegener’s granulomatosis (>90% positive predictive value).
- Polyarteritis nodosa
- Necrotising vasculitis.
- Inflammatory bowel disease.
- Systemic lupus erythematosus.
- Rheumatoid arthritis.
p-ANCA is not specific but these are seen in:
- Polyarteritis nodosum.
- Primary sclerosing cholangitis.
- Microscopic polyangiitis.
- Ulcerative colitis.