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.

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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