Arthritis facts

Arthritis explained: the lowdown on pathology and arthritis

In Australia, 1 in 6 people have some form of arthritis and it can be diagnosed in children or adults. In partnership with Arthritis Australia, here’s an update from immunopathologist A/Prof Stephen Adelstein on arthritis types and tests.

What is arthritis?

Arthritis is a name for a group of conditions affecting the joints. Symptoms of arthritis include pain, stiffness or reduced movement of a joint, swelling in a joint, redness and warmth in a joint. People may also experience general symptoms such as tiredness, weight loss or feeling unwell.

What tests are there for arthritis and autoimmune disorders?

When diagnosing arthritis, a doctor will first ask you about your symptoms and may examine you for signs of arthritis or other autoimmune features. Then pathology tests may be performed to:

  • Confirm a diagnosis of arthritis or another autoimmune disorder
  • Monitor disease activity and response to treatment
  • Check for side effects from medicines you are taking

Are all types of arthritis diagnosed by blood tests?

Most forms of arthritis can be diagnosed by blood tests. The doctor may use blood tests to support a diagnosis made on the signs and symptoms, or to rule out a different type of arthritis or other condition with similar symptoms. Pathology tests may not be required to diagnose some conditions such as osteoarthritis or chronic back pain. This article focuses on those conditions where pathology tests are used to assist with diagnosis. For more information about osteoarthritis check out this page from Arthritis Australia.

Blood tests

Erythrocyte Sedimentation Rate (ESR): ESR tests measure the level of inflammation in the body but do not determine 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 amount of C-reactive protein in the blood, which shows the level of inflammation in the body. The test is not specific enough to diagnose a particular type of arthritis or disease, so 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 several conditions can give positive RF results. People without RA can also test positive for RF, particularly older people, but this does not mean they will develop the condition.

Anti-Cyclic Citrullinated Peptide antibody (anti-CCP):  Anti-CCP antibodies (proteins made by the body’s immune system) are commonly present in people with RA. This test is useful in the early stages of RA or in borderline cases, as it is a stronger indicator of RA than the rheumatoid factor test. As not all people with early RA test positive, the doctor will use other tests and examinations so the diagnosis is more reliable.

Antinuclear Antibody (ANA): The ANA test is used to screen for autoimmune disorders. In particular, almost 100% of people with systemic lupus erythematosus (SLE) have a positive ANA test. People with conditions such as Sjögren’s syndrome, scleroderma, Raynaud’s disease and rheumatoid arthritis can also have a positive ANA result, so further testing, plus the patient’s symptoms and signs, is usually needed for a final diagnosis.

  • Anti-dsDNA test: This test helps diagnose and monitor SLE. It is ordered after a positive ANA test to confirm a diagnosis of SLE.
  • Extractable Nuclear Antigen Antibodies (ENA) panel: This test comes after a positive ANA test to help diagnose a specific autoimmune disorder. The number of tests done on the blood sample will depend on the clinical symptoms and the doctor’s assessment.

HLA typing: This test looks for the presence of certain genetic markers in the blood that are associated with an increased risk of developing certain types of arthritis.

Uric Acid test: Levels of uric acid in the blood are measured to test for gout. As high levels of uric acid can occur in people without gout, other tests (arthrocentesis, X-ray and ultrasound) might be needed to confirm diagnosis.

Other pathology tests

Arthrocentesis: Arthrocentesis is the process of extracting some fluid from a joint, usually using a needle and syringe. Although infections can be identified with a blood test, arthrocentesis, if possible, is usually better. It is also the most specific test for gout.

  • The fluid is cultured to check for an infection.
  • The fluid is observed under a polarised microscope to look for uric acid crystals to check for gout.

Forms of arthritis diagnosed by pathology tests

Autoimmune disorders

Rheumatoid Arthritis (RA): A common inflammatory form of arthritis that causes pain and swelling of the joints and other organs in the body, such as the lungs and skin. In RA, the immune system attacks healthy tissues, specifically the lining of the joints, causing inflammation and joint damage.

Spondyloarthritis: Includes inflammatory diseases that involve both the joints and the entheses (the sites where the ligaments and tendons attach to the bones; for example, around joints, at the edges of the vertebral bodies of the spine and where tendons attach to the heel bone).

  • Ankylosing Spondylitis (AS): The most common symptoms of AS are chronic pain and stiffness in the lower back, buttocks and hips. AS usually develops slowly over several weeks or months.
  • Reactive arthritis: Reactive arthritis follows certain infections. The most common symptoms are inflammation in the joints, eyes and urethra (the tube that helps remove urine from the body). Mouth sores and skin rashes sometimes occur.
  • Psoriatic Arthritis (PsA): Approximately 30% of people with psoriasis (a skin condition characterised by itchy, scaly rashes and crumbling nails) also develop PsA. The symptoms of PsA include joint pain and stiffness, skin rashes, nail changes, fatigue, eye problems, and swelling and tenderness in fingers and feet. PsA may be indistinguishable from other types of arthritis, except that the patient has psoriasis.

Systemic Lupus Erythematosus (SLE):  The immune system attacks healthy tissues, including the joints and skin. In some people, the lungs, kidneys, blood vessels, brain or other parts of the body are also affected.

Sjögren’s syndrome: Abnormal dryness of the mouth, eyes and/or other tissues. Around half the people who have Sjögren’s syndrome also have another form of arthritis

Scleroderma:  Scleroderma affects the connective tissues of the body (tissues that hold together joints, muscles, blood vessels and internal organs), causing skin thickening. Many different areas of the body can be affected. Raynaud’s phenomenon is common in people with scleroderma.

Raynaud’s disease: Raynaud’s phenomenon is a condition that can cause discomfort as the blood supply to the fingers and toes becomes reduced. When this happens, the person’s fingers or toes change colour. It can happen in cold temperatures or emotionally stressful situations.

Inflammation and other forms of arthritis

Septic arthritis: Some infections can lead to joint destruction and this occurs much quicker than with other forms of arthritis. It is crucial to rule out an infection when arthritis affects a single joint.

Gout: A common and painful condition that affects the joints and tendons. Small crystals of uric acid form in and around the joint which causes inflammation, pain and swelling. An attack of gout usually comes on very quickly, often overnight. The joint becomes red, swollen and painful. It often affects one joint at a time, such as the big toe.