The C ANCA blood test is used to determine if there are autoantibodies being produced by a person’s immune system. The immune system usually creates antibodies to ward off an invasion of bacteria, viruses, and other pathogens, but sometimes it turns its attention inward and mistakenly attacks the body instead. If an autoimmune disorder is suspected by a medical provider, then this blood test will be ordered.
It is most commonly ordered when someone presents with the signs and symptoms of an inflammatory bowel condition. This may include Crohn’s disease or ulcerative colitis. It may also be ordered to determine if an autoimmune version of vasculitis. Abdominal pain, bleeding during a bowel movement, and ongoing fatigue are common symptoms that will be evaluated. Some individuals may experience joint pain.
Vasculitis also has a specific symptom set that may trigger the C ANCA blood test being ordered. This includes protein in the urine, skin rashes, flu-like symptoms that don’t go away, hear loss, or itchy eyes that do not improve.
What Do My C ANCA Blood Test Results Mean?
The results of this blood test must be measured against an individual’s medical history to determine a specific result. In general, however, a positive or negative test result is generally communicated based on the signs and symptoms that were presented to a medical provider. For a positive C ANCA blood test, this typically means that there are PR3 antibodies that have been detected during the test. A positive test will generally require a second test to determine the level of antibodies that are present.
If the C ANCA blood test is negative but other tests, such as the ASCA blood test, come back as positive, then this is typically an indication that Crohn’s disease is present. It the C ANCA blood test is positive, but the ASCA blood test is negative, then this is a general indication that ulcerative colitis is present. Both tests can still be negative, however, and an inflammatory bowel condition could still be present.
Certain vasculitis conditions are also likely with a positive test result. 90% of people with an active Wegener granulomatosis, for example, will have a positive C ANCA blood test. Up to 70% of people with an inactive version of the disease will also have antibodies present during the test. 3 out of 10 people with microscopic polyangiitis will also have a positive C ANCA blood test.
If a positive blood test does come back, the next step is typically the ordering of a biopsy. This will let medical providers understand more about an individual’s specific condition so that a treatment plan may be developed.
Here’s What You Need to Know
Once an individual has developed autoantibodies that can be detected by the C ANCA blood test, they are never going to go away. The concentration levels of the autoantibodies can help medical providers understand whether or not a suspected or diagnosed condition has relapsed. Early testing, however, may come back with a false negative because the autoantibodies have not yet fully developed.
Most local laboratories do not have the capability to perform the C ANCA blood test. The blood draw is usually sent to a clinical laboratory for measurement, which means results may be delayed by up to 3-5 business days depending on patient location.
The C ANCA blood test is not ordered for everyone. It is only ordered by a medical provider when vasculitis or an inflammatory bowel condition are suspected because of presenting signs and symptoms. The average person will never have this blood test ordered for them as a gauge of their overall health.
Certain conditions may create a false positive on this blood test as well. A positive C ANCA blood test can happen when there is a heart or respiratory infection, rheumatoid arthritis, lupus, or certain forms of hepatitis. Many autoimmune disorders are also known to cause systemic vasculitis and some of these conditions may overlap. A treatment plan may involve treating the positive test results and co-existing conditions that may be contributing to the signs and symptoms being experienced.
Although the autoantibodies do not go away once they’ve been developed, the C ANCA blood test can help a medical provider create an effective treatment plan. If you have the symptoms that could indicate the presence of vasculitis of an inflammatory bowel issue, then schedule an appointment and discuss the benefits of having this test done. It could be the first step taken on a journey that leads toward relief.