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Antineutrophil Cytoplasmic Antibodies (ANCA, MPO, PR3)

Also Known As:  ANCA Antibodies, cANCA. pANCA. Serine Protease 3. MPO, PR3, Anticytoplasmic Autoantibodies, 3-ANCA, PR3-ANCA, MPO-ANCA, Myeloperoxidase Antibodies, Proteinase 3 Antibodies

Test Panel: C-Reactive Protein (CRP), Complementm Urinalysis, Anti-Saccharomyces cerevisiae Antibodies (ASCA), Calprotectin,
Lactoferrin

ANCA

Why Get Tested:

  • 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 case of vasculitis and in inflammatory bowel disease.

When to Get Tested:

  • When you have symptoms such as fever, muscle aches, and weight loss or impaired kidney or lung function that your healthcare practitioner thinks may be due to a vascular autoimmune disorder.
  • When you have symptoms such as persistent or intermittent diarrhea and abdominal pain that your healthcare practitioner suspects may be due to an IBD; when your healthcare practitioner wants to distinguish between CD and UC.

Sample Required:

  • 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 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.
    1. Two types of staining pattern seen for two different antibodies.
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Types of ANCA

  1. When patient sera are incubated with alcohol-fixed neutrophils, indirect immunofluorescence shows two patterns:
  2. 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 ).
    1. In respiratory disease, it is present in only about 65 % of the cases.
    2. All Wegner’s patients with limited disease in the kidney are not positive for c-ANCA.
    3. When Wegner’s is not active then % drops to 30%.
    4. A negative result for c-ANCA does not rule out Wegener’s.
    5. False positive results are rare.
    6. Rising titer for c-ANCA suggests relapse.
      1. When titer is falling indicates successful treatment.
  3. p-ANCA (perinuclear ANCA)  produces a perinuclear pattern of staining in the neutrophils cytoplasm. 
    1. It is found in about 50% of the patient with kidney disease.
    2. This is also positive (about 75%) in other autoimmune diseases like Ulcerative colitis or sclerosing cholangitis.
  4. c-ANCA appears to have anti-proteinase 3 specificity, while p-ANCA has predominantly anti-myeloperoxidase activity.
    1. Result: Negative when there is very little fluorescence or no fluorescence.

Lab diagnosis

  1. Serological method for the detection of ANCA.
    1. Detection of c-ANCA is sensitive and specific for the diagnosis of Wegener’s disease.
  2. A biopsy is more diagnostic.

Normal values:

  • Serological method
    • Not found normally in the serum.
      • Negative = <1:20
  • 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.
      1. Not all p-ANCA cases are positive for MPO.

Increased level is seen in:

  • 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.



Possible References Used


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