ANCAs, short for antineutrophil cytoplasmic antibodies, are a kind of autoantibody. They are the opposite of antibodies, which the immune system produces to fight germs. ANCA autoantibodies attack the healthy tissues in our...
Introduction
ANCAs, short for antineutrophil cytoplasmic antibodies, are a kind of autoantibody. They are the opposite of antibodies, which the immune system produces to fight germs. ANCA autoantibodies attack the healthy tissues in our body and damage them. ANCAs attack neutrophils, the white blood cells, which our immune system uses to fight infections.
When one has autoantibodies in the blood it means that person could have an autoimmune disease.
The ANCA test is a blood test that checks for proteins made by our immune system to fight against infections. The findings of this test enable doctors in distinguishing ulcerative colitis from Crohn's disease. The ANCA test can also assist a physician diagnose autoimmune diseases like vasculitis, which is a form of blood vessel disease.
Understanding the ANCA test and why it is done
The ANCA test is useful in examining two main types of ANCAs, each of which attacks a different protein inside our WBC (white blood cells):
The pANCA focuses on a protein called myeloperoxidase (MPO), while the cANCA focuses on a protein called proteinase 3 (PR3).
There are two types of ANCA tests:
- IIF or Indirect immunofluorescence: In this test the blood sample of the patient is mixed with neutrophils on a slide. After that, a special stain has to be added to highlight the autoantibodies. If the blood of the patient contains ANCAs, they will get attached to the neutrophils, forming a pattern that is visible under a microscope. Each p-ANCA and c-ANCA creates a pattern different from each other.
- ELISA or Enzyme-linked immunosorbent assay: The purpose of this test is to check the blood for antibodies to MPO and PR3. An ELISA test can predict if one has pANCA or cANCA.
When to get an ANCA test done?
One of the main reasons to undergo an ANCA test is when the doctor isn’t sure whether a patient has Crohn's disease or ulcerative colitis, which are types of inflammatory bowel diseases (IBD). It is because the symptoms of these two diseases are almost identical and it is very hard to differentiate.
Inflammatory bowel diseases (IBD) can be diagnosed with a combination of different tests. One is through blood tests and physical examination.
Another test is EGD or Esophagogastroduodenoscopy. In this test, the doctor places a scope into the upper GI tract of the patient to investigate changes in the esophagus, the top of the small intestine, and the stomach.
It can also be tested with colonoscopy, a test in which a scope is placed into the lower GI tract to observe any changes in the large intestine and rectum.
The doctor would ascertain if a patient had chronic diarrhea for over four weeks to make the diagnosis of ulcerative colitis. They would also check to confirm if the patient has active inflammation and chronic changes on a biopsy done during a colonoscopy.
However, at times, these tests aren’t very successful in confirming which type of IBD a patient has. An ANCA test is a method that helps the doctor to figure out whether it is ulcerative colitis or Crohn's disease in case of ambiguous findings.
It has been observed that almost 80 percent of people with ulcerative colitis test also become positive for pANCA.
Researchers have also found that PR3 protein is much more common in children with ulcerative colitis compared to people with Crohn's disease.
The ANCA test is also beneficial in predicting whether or not a patient will respond to IBD medicines—called TNF (tumor necrosis factor) inhibitors. TNF inhibitors can block a protein made by the immune system that causes inflammation in the intestine.
Moreover, the most common use of an ANCA test is to diagnose vasculitis. This is a cluster of autoimmune disorders that impact the small blood vessels. In this disorder, ANCAs attach to neutrophils and force them to attack the blood vessels. As a result of this attack, there is swelling of the blood vessels.
There are three types of vasculitis associated with ANCA:
- EGPA (Eosinophilic granulomatosis with polyangiitis): It is inflammation of blood vessels in the heart and kidneys.
- Granulomatosis with polyangiitis aka Wegener granulomatosis: It affects blood vessels in the lungs and kidneys.
- MPA (Microscopic polyangiitis): It impacts blood vessels in the kidneys, lungs, skin, and joints.
Vasculitis can cause different symptoms and it depends on which blood vessels it affects. For instance, there will be a rash when it inflames blood vessels in the skin, but when it attacks the kidneys it will result in foam or blood in the urine.
Moreover, the ANCA test is very useful in diagnosing vasculitis if a person has the following symptoms:
- Fever
- Weight loss
- Tiredness
- Vision or hearing loss
- Muscle or joint aches
- Skin rashes or sores
- Blood stains in the urine or urine that appears foamy
The ANCA test can also predict whether the vasculitis treatment one is undergoing is effective or not. The physician, with the help of an ANCA test, can tell whether there will be a recurrence of the symptoms after the treatment.
Conducting an ANCA test
So, how is an ANCA test conducted? There are no special arrangements needed for the ANCA test and the consulting doctor will apprise the patient with all the details of the procedure. If there is another blood test that needs to be done along with the ANCA test, then the patient might have to fast for eight to 12 hours before the test.
It can be done anywhere, in the lab, in a clinic, or at the doctor’s chamber. Blood will be drawn from the arm and will be sent to the lab for testing. If you want to know more about the c-ANCA and p-ANCA test talk to your doctor for more accurate information.
Conclusion
The results of the ANCA test may take a few days to come. If one has got a positive test, he or she may have an autoimmune vasculitis. The type of ANCA will help to ascertain which autoimmune vasculitis a person has. And one may have both types of ANCA.
If a person has symptoms of IBD, then a positive result may indicate that it is more likely ulcerative colitis rather than Crohn's disease. Research shows that around 80% of people with ulcerative colitis will have an ANCA test that is positive.
Once the results come, the consulting doctor will talk to the patient and explain the interpretation and will also discuss the future course of action. It might be a few more tests or a particular treatment.
FAQs
What is C-Anca and P-ANCA?
When indirect immunofluorescence is used on ethanol-fixed neutrophils, two major fluoroscopic patterns come out, one is diffuse cytoplasmic staining (C-ANCA), and the other is perinuclear/nuclear staining (P-ANCA).
What is the difference between p-ANCA and c-ANCA vasculitis?
There are two main kinds of autoantibodies involved in ANCA vasculitis. One is known as P-ANCA (perinuclear ANCA), which is a type of autoantibody that usually targets and attaches to something called MPO (myeloperoxidase), which is inside neutrophils. Another type is known as C-ANCA (cytoplasmic ANCA), which typically specifically binds to a substance called proteinase 3 (PR3) found within neutrophils.
What does a positive C-Anca test imply?
If the ANCA results are negative, then it means that the person doesn’t have autoimmune vasculitis and positive results imply that one may be diagnosed with autoimmune vasculitis.
What is a C-Anca blood test?
An ANCA test is a type of blood test that examines proteins produced by the immune system to combat infections. This test enables doctors to distinguish ulcerative colitis from Crohn's disease. Further, it can also assist the physician to diagnose autoimmune diseases like vasculitis, a blood vessel disease.
What is the treatment for C Anca?
Acute c-ANCA (cytoplasmic antineutrophil cytoplasmic antibody) positive vasculitis is usually treated with cyclophosphamide and corticosteroids.
Is ANCA curable?
Vasculitis can be cured very quickly in some cases. But in some other cases, when the disease becomes chronic, treatments markedly reduce disease activity, followed by periods in which therapies become less effective and symptoms reappear.
What are the symptoms of ANCA?
Common signs of ANCA include unintentional weight loss, fever, reduced or complete loss of appetite, symptoms resembling the flu, night sweats, and an overall sense of weakness or unease. This condition is known as malaise.
Can you live a normal life with vasculitis?
Vasculitis may be a rare condition with difficulty in diagnosing, but, many people with vasculitis recover and usually live healthy, normal lives. Hence, proper diagnosis and better treatment are necessary to thwart long-term or significant damage to the impacted organs.
Can vasculitis be cured permanently?
Currently, there is no known cure for vasculitis. However, the key to managing the condition lies in early detection and treatment, which can greatly alleviate symptoms and prevent the disease from advancing further.
