Arthritis Blood Tests for Diagnosis
The diagnosis of arthritis is made by putting together clinical clues. History and symptoms will provide most of the information needed, but imaging and laboratory tests will confirm the diagnosis.
Some types of arthritis, such as rheumatoid arthritis, have more sensitive and specific blood tests than other types of arthritis. Blood tests are not a 'stand alone' diagnostic tool for any type of arthritis. Rather, they provide another piece of the puzzle in the context of clinical history.
Blood Tests for Osteoarthritis
Blood tests are not used to diagnose osteoarthritis.
Osteoarthritis (OA), or degenerative joint disease, is characterized by inflammation, swelling and destruction of the joint spaces. There are no specific blood tests that mark osteoarthritis, but those tests that show inflammation can potentially be elevated in OA, although usually not.
Blood tests are not used to follow OA, but elevated levels of inflammatory indicators may be noted when blood is checked for other reasons. Symptoms, history and X-rays when needed are the tests used for this condition.
Types of Arthritis
Different types of arthritis, when suspected based on history and physical exam, will lead the practitioner down different paths for diagnosis.
An older person with aching joints and increasing disability is more likely to have osteoarthritis. This may be determined from history and physical alone, or more often in conjunction with X-rays of problematic joints.
Osteoarthritis causes increased indicators of inflammation in the body. These tests are not diagnostic of osteoarthritis, though. This means they are non-specific blood tests that are elevated in the blood when there is inflammation somewhere in the body.
Other autoimmune diseases, such as lupus, ulcerative colitis, sjogren's syndrome and many others may have joint inflammation - arthritis - as a component of disease.
Rheumatoid arthritis presents more often in younger patients. As an autoimmune disease, rheumatoid arthritis causes joint damage, pain and disability.
Diagnosis of Rheumatoid Arthritis
Blood Tests for Rheumatoid Arthritis
Rheumatoid arthritis (RA) is an autoimmune disease. This means that the body's immune system mistakes normal body tissue or organs for something that shouldn't be there. When the immune system attacks germs or foreign material, it is able to destroy and eliminate it from the body. This is its normal function. In rheumatoid arthritis, the immune cells attack joints and often other parts of the body causing a variety of symptoms. Joint pain, stiffness and swelling are the 'arthritic' manifestation of this damage.
As stated earlier, no blood test will reliably diagnose rheumatoid arthritis, but there are some that are highly suggestive of the disease, especially in the right clinical setting.
RHEUMATOID FACTOR was considered the most sensitive and specific blood test for rheumatoid arthritis for a long time. Rheumatoid factor is measured in a simple blood test. The laboratory and your doctor can help you compare your level with normal levels.
Rheumatoid factors are antibodies. A rheumatoid factor level can be elevated in other disorders as well, such as Sjogren's syndrome or lupus, and can be absent in rheumatoid arthritis, so it's important to have your doctor, often a rheumatologist along with your regular doctor, help put your symptoms and test results together before arriving at a diagnosis.
Another newer antibody test is the ANTI-CCP antibody (anti cyclic citrullinated peptide). Anti-CCP has been found to be more accurate for both diagnosis and prognosis of rheumatoid arthritis. This means that if you have anti-CCP, you very likely have RA. Also, the higher the level, the more severe the disease is, or could be in the future.
Other blood tests like CRP (C-reactive protein) and ESR (erythrocyte sedimentation rate) can also be elevated in RA, but are in no way diagnostic or specific for this condition. They are elevated in many inflammatory, infectious and autoimmune disorders.
Other Blood Tests Useful in Arthritis
CBC: This stands for "complete blood count". The white blood cell count is a marker of infection or inflammation, and therefore may be elevated in various types of arthritis.
ANA: The anti-nuclear antibody test may be ordered when lupus or other autoimmune disorders are suspected. The ANA is most often elevated in lupus, but is also found in other diseases, and sometimes in normal people (about 5 percent).
HLA-B27: This test is used to confirm a diagnosis of ankylosing spondylitis, a specific type of arthritis of the spine. HLA-B27 is also elevated in psoriatic arthritis and reactive arthritis.
ESR: The erythrocyte sedimentation rate is another non-specific marker of inflammation. It is elevated with both acute and chronic inflammation, autoimmune conditions and cancer.
CRP: C-reactive protein may be elevated in inflammation and bacterial infections.
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