Psoriatic arthritis (PsA) is an autoimmune condition whereby the immune system attacks healthy tissue, particularly the lining of the joints, causing inflammation. This causes joints to become painful, stiff and often swollen. People who develop PsA often also have psoriasis, a skin condition that causes thick silvery scales or dry, red patches of skin to form.
To help determine if you have PsA or another medical condition you will be assessed by your doctor and undergo a range of tests, including blood tests. Blood tests alone cannot confirm a PsA diagnosis. Blood tests can show signs that may indicate PsA, as well as help rule out other conditions. Physical signs and symptoms of PsA, such as pain, fatigue and psoriasis cannot be detected in a blood test and require physical examination. Your doctor will also want you to have imaging tests done to help detect damage to the bone and/or joint. Your doctor will use evidence from all tests to make a PsA diagnosis.
What are blood and pathology tests used for?
- Show signs that may indicate arthritis or another autoimmune disorder
- Monitoring disease activity and your response to treatment
- Checking for side effects from your medicines
Types of blood tests
Erythrocyte Sedimentation Rate (ESR): ESR tests measure the level of inflammation in the body. However, the test does not reflect exactly where in the body the inflammation is or what is causing it. ESR can also be affected by other conditions besides inflammation, so it is used alongside other tests
C-Reactive Protein (CRP): CRP tests measure the level of inflammation in the body by measuring the amount of C-reactive protein in the blood. The test is not specific enough to diagnose a particular type of arthritis or disease, so it is used alongside other tests.
Rheumatoid Factor (RF): The RF test is commonly used to help diagnose rheumatoid arthritis (RA). However, a positive RF test does not always mean a person has RA, as there are several conditions that give positive RF results. Healthy people without RA can also test positive for RF, particularly older people. This does not mean they will develop the condition.
Anti-Cyclic Citrullinated Peptide antibody (anti-CCP): Like RF, the anti-CCP antibodies (proteins made by the body’s immune system) are commonly present in people with rheumatoid arthritis (RA). This test can help rule out RA as it is a stronger indicator of RA than the RF test.
Antinuclear Antibody (ANA): The ANA test is used to screen for autoimmune disorders. A positive ANA test result may suggest an autoimmune disease such as PsA, but further testing, along with the patient’s symptoms and signs, is usually needed to make a final diagnosis.
HLA-B27: A gene called HLA-B27 is associated with PsA, especially inflammation of the spine. You doctor may suggest you have a blood test to find out if you have this gene. However, there are many people who have this gene and do not get PsA.
Does Medicare cover the cost?
The costs of different types of blood tests may vary, but Medicare generally covers all or part of the cost for blood tests. Most blood tests are bulk-billed, so you don’t have to pay anything. Check with your doctor about how much the blood test will cost and whether Medicare will cover the full or partial amount.
CONTACT YOUR LOCAL ARTHRITIS OFFICE FOR MORE INFORMATION ON ARTHRITIS.
This resource has been developed based on the best available evidence. A full list of references is available upon request.