Tests & Diagnosis
No single form of testing will confirm a rheumatoid arthritis diagnosis; instead, a diagnosis must be made using a variety of techniques, and often involves as much a process of ruling out other diseases, as confirming RA itself.
A classification system for RA-specific diagnostic criteria has been developed which will help your physician identify a likely RA diagnosis.
Patients who experience any four of the following seven symptoms – simultaneously, or one after the other in any period of time – can be considered to have rheumatoid arthritis:
- At least one hour of morning stiffness in an around joints prior to improvement
- Swelling in the soft tissue of three or more joints, for at least six weeks (supported by observation from a physician)
- Swelling in the fingers, knuckles and wrists, for at least six weeks
- Swelling that appears symmetrically (in both left and right joints) for at least six weeks
- Bumps (nodules) under the skin
- Positive test for rheumatoid factor
- Positive test for anti-ccp antibody
- Bone erosion, thinning of bone, or reduction of bone mass in the hand or wrist joints, detectable via x-ray
Laboratory blood tests may reveal the presence of antibodies (rheumatoid factor, anti-ccp), proteins manufactured by the body’s immune system that are often present in RA.
Not all patients with a positive rheumatoid factor will have RA.
Many chronic diseases (ie: hepatitis C) will give an elevated rheumatoid factor. Patients that have a positive anti-ccp antibody often will have a more aggressive form of rheumatoid arthritis.
In addition to revealing a person’s rheumatoid factor and anti-ccp, laboratory findings will indicate the following:
- ESR – Erythrocyte sedimentation rate, which indicates the rate at which red blood cells sediment, a measure of inflammation. ESR will be elevated in cases of rheumatoid arthritis
- CRP – C-reactive protein, a protein found in the blood, the levels of which rise in response to inflammation from rheumatoid arthritis.
- ANA – antinuclear antibody, a protein manufactured by the immune system that is directed against an individual’s own cells, which are detected in about one-third of RA patients.
High platelet counts in the blood (thrombocytosis) and a decrease in the red blood cell count (anemia) can also be indicative of RA.
Over time, X-rays will reveal many of the features of rheumatoid arthritis, including:
- Abnormal joint alignment
- Reduced bone mass or thinning around the joints
- Symmetrical loss of joint-space
- Bone deformities
- Bone loss or erosion
- Swelling of soft tissue, including non-calcified nodules
These manifestations will often take months to develop, so patients presenting with typical symptoms of RA should maintain regular visits with their physician early on.
Rheumatoid arthritis must be diagnosed clinically, based on these specific signs and symptoms; a large number differential (other) diagnoses must be ruled out due to their similarity with the symptoms of RA. Some of the more common differential diagnoses may include:
- Psoriatic arthritisand other seronegative sponyloarthropathies
- Polymyalgia rheumatica
- Viral infection