|
Page: Diagnosis
Main article
| Home > Arthritis > Diagnosis |
Diagnostic criteria
The American College of Rheumatology has defined (1987) the following criteria for the classification of rheumatoid arthritis:
* Morning stiffness of >1 hour.
* Arthritis and soft-tissue swelling of >3 of 14 joints/joint groups
* Arthritis of hand joints
* Symmetric arthritis
* Subcutaneous nodules in specific places
* Rheumatoid factor at a level above the 95th percentile
* Radiological changes suggestive of joint erosion
At least four criteria have to be met for classification as RA.
It is important to note that these criteria are not intended for the diagnosis of patients for routine clinical care. They were primarily intended to categorise patients, for research. For example: one of the criteria is the presence of bone erosion on X-Ray. Prevention of bone erosion is one of the main aims of treatment because it is generally irreversible. To wait until all of the ACR criteria for rheumatoid arthritis are met is therefore likely to result in a worse outcome for the patient. Most patients and rheumatologists would agree that it would be better to treat the patient as early as possible and prevent bone erosion from occurring, even if this means treating patients who don't fulfill the ACR criteria. The ACR criteria are, however, very useful for categorising patients with established rheumatoid arthritis, for example for epidemiological purposes.
Blood tests
When RA is being clinically suspected, immunological studies are required, such as rheumatoid factor (RF, a specific antibody). A negative RF does not rule out RA; rather, the arthritis is called seronegative. During the first year of illness, rheumatoid factor is frequently negative. 80% of patients eventually convert to seropositive status. RF is also seen in other illnesses, like Sjo"gren's syndrome, and in approximately 10% of the healthy population, therefore the test is not very specific.
Because of this low specificity, a new serological test has been developed in recent years, which tests for the presence of so called anti-citrullinated protein antibodies (ACPA). Like RF, this test can detect approximately 80% of all RA patients, but is rarely positive in non-RA patients, giving it a specificity of around 98%. In addition, ACP antibodies can be often detected in early stages of the disease, or even before disease onset. Currently, most common test for ACP antibodies is the anti-CCP (cyclic citrulinated peptide) test.
Also, several other blood tests are usually done to allow for other causes of arthritis, such as lupus erythematosus. The erythrocyte sedimentation rate (ESR), C-reactive protein,[6] full blood count, renal function, liver enzymes and other immunological tests (e.g. antinuclear antibody/ANA) are all performed at this stage. Ferritin can reveal hemochromatosis, which can mimic RA.
|
Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
|