How is rheumatoid arthritis diagnosed?

Rheumatoid arthritis can be notoriously difficult to diagnose, especially in its early stages. Stiff, painful joints are usually among the first symptoms of RA, but occur in many other joint diseases.

• As with OA, the first step is for a doctor to take your medical history.
• The answers to certain questions, like "Which joints are giving you trouble?" or "Do the joints feel stiff in the morning and, if so, how long does the stiffness last?" can help a doctor narrow the list of possible joint problems.

• The doctor will focus on the affected joints, looking for the telltale signs of RA: joints with a limited range of motion that are tender, reddened, swollen or warm.
• As noted earlier, problems in symmetrical joints — both elbows, for example — increase the odds that RA is present.

• Only one laboratory test is useful for confirming a diagnosis of RA: the rheumatoid factor test.
• Rheumatoid factor is an antibody produced by the synovial membranes of joints affected by RA, and can be found in the blood of 80 to 90 per cent of people with the condition. (Unfortunately, rheumatoid factor is often absent in the early stages of RA — when the test's help in diagnosing the disease is most needed.)
• In general, patients who test positive for rheumatoid factor tend to have more severe RA than those who test negative, and people with high levels of rheumatoid factor are more acutely affected than those with low amounts.

• Another test, the erythrocyte sedimentation rate, or "sed rate," is a broad indicator of inflammation in the body, including RA.
• Inflammation tends to make red blood cells sticky, so they form clumps that will settle ("sediment out") in a test tube.
• The greater the inflammation, the larger the red-cell clumps and the faster they'll fall to the bottom of the tube.
• This makes the sed rate useful for monitoring whether a treatment for RA is reducing inflammation.
• But because infections, malignancies and other problems can provoke inflammation, the sed rate is not useful for initially diagnosing the condition.

• A useful but more invasive way to confirm that a person has some form of inflammatory arthritis is to evaluate synovial fluid removed from an affected joint by use of a needle.
• The fluid is examined for neutrophils, which are the white blood cells that gather at sites of inflammation.

• These are not the best way to diagnose RA. They often appear totally normal early in the course of the disease, even when symptoms are severe.
• In fact, X-rays usually don't provide evidence of RA until significant and irreversible joint damage has occurred.
• At that point, X-rays reveal that inflammation has destroyed cartilage and eroded the underlying bone.