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

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.

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