A firm diagnosis of rheumatoid arthritis can be made when the patient fulfils four out of seven specified American College of Rheumatology (ACR) criteria.
However, the diagnosis may be tentatively made on the basis of clinical suspicion, even if these criteria are not present.
The diagnosis does not require use of blood tests or X-rays. It is a mistake to discount the diagnosis on the basis of normal investigations. The clinical examination is the most important aspect of assessment of the problem.
No specific tests
There are no specific tests for rheumatoid arthritis. A positive Rheumatoid Factor is found in less than 85% of patients with the disease. These patients are termed seropositive.
The test is negative in many patients, where it is termed seronegative. Although its presence does not establish the diagnosis, high levels of Rheumatoid Factor may predict a more severe and progressive disease, often with non-joint manifestations.
In addition, the test may be positive in other conditions and in the elderly. Once shown to be present, there is no value in repeated testing. A new antibody test, anti-CCP antibodies, has been shown to be more specific and useful in the diagnosis of early rheumatoid arthritis.
Those with active rheumatoid arthritis often have anaemia. The erythrocyte sedimentation rate (ESR) is increased in many patients with active disease, as is the C-reactive protein, (CRP). These markers of inflammation are useful when raised as they can be used to monitor progress.
Role of X-rays
X-rays are not always useful early in the disease, revealing mainly swelling of the soft tissues around the joint and fluid in the joint space.
However, the early appearance of erosion of bone around the joint margin indicates a more aggressive disease process and should prompt more aggressive treatment.
As the disease progresses, the abnormalities become more obvious, with narrowing of joint space and damage to joint margins. X-rays are useful in monitoring progress as they provide independent information as to the patient's response to particular therapy.
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Reviewed by Dr Dr I C Louw, Rheumatologist/Physician and Dr A Halland, Rheumatologist/Physician, March 2007