Diagnosis of Rheumatoid arthritis

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It can be difficult to diagnose RA as there are very many causes of joint inflammation, but RA is the most common cause. Diagnosis will largely depend on your medical history.

Your doctor will ask you about all your symptoms and how long you have had them. Your joints will then be examined to see if they are swollen and to find out how easily they move. Symptoms usually start slowly.

Blood Tests- Your doctor will then arrange for a blood test.

If you have RA you may have a protein in your blood called rheumatoid factor. Approximately 80% of people with rheumatoid arthritis have positive tests for this protein. However approximately 5% of people without rheumatoid arthritis also test positive and only half the people with RA test positive in the early stages of the condition.

A blood test may also show that you are anaemic, which affects the majority of people with RA. Other blood tests may also show changes in your blood, which are produced by inflammation (erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP)).

Citrullinated peptide (anti-CCP) is a new blood test, which measures certain specific antibodies. This can confirm your diagnosis and also may indicate whether you are at increased risk for damage to the joints. Tests may also be done to identify the different types of antibodies in your blood (an antibody study). Your body normally produces antibodies to attack bacteria, viruses etc. but as RA is a disease where the immune system is disturbed (an autoimmune diseases) antibodies can attack your body's own tissues, so this study is commonly requested.

Your doctor will probably also arrange for X- rays of your joints to see if they reveal any damage caused to the joints by the inflammation of RA. Magnetic resonance imaging (MRI) scans are more sensitive than X-rays and may show signs of joint damage earlier than other tests. However it is not necessary for your doctor to do these to make the diagnosis.

If four or more of the signs are positive it is very likely that you have RA.

Morning stiffness that lasts for more than an hour for more than 6 weeks
Inflammation and swelling of three or more joints, for more than six weeks
Swelling and inflammation of your hand joints, for more than six weeks
Symptoms in the same joints on both sides of your body (symmetrical arthritis), for more than six weeks
Rheumatoid nodules are present
Positive test for rheumatoid factor in your blood
X- rays, showing changes in your joints

Your specialist will probably wish to assess the severity of your condition by checking the Disease Activity Score (DAS).

This is done by:

Looking at certain specific joints for swelling and tenderness,
Asking you to give a global score of how you feel (the Visual Analogue Score, or VAS), and
Checking your ESR or CRP (from your blood test)