Blood tests or imaging studies to diagnose rheumatoid arthritis do not help to pinpoint the diagnosis, especially in the early stages. There are more than a hundred types of arthritis and this makes it that much more difficult.
Rheumatoid arthritis is a chronic inflammatory disorder that causes pain, swelling, and stiffness in the joints. The joints usually affected are those of the hands, feet, and wrists.
There may be periods where symptoms go into remission or they become worse and flare up. These periods of acute symptoms flaring up are known as flare-ups or flares.
With treatment, it’s possible to reduce the frequency of flares and minimize or prevent long-term damage to the joints.
The real help to diagnose rheumatoid arthritis comes from the signs and symptoms elicited from the clinical history and examination. The doctor then proceeds to diagnose rheumatoid arthritis with blood tests and imaging studies, which also help to determine the extent of the damage to the involved joints.
For example, higher levels of rheumatoid factor (RA factor) in the blood indicate a higher level of inflammation.
Your doctor, ideally a rheumatologist, will take a detailed history of your symptoms and examine the joint for the classic signs, which will help him to diagnose RA. These include:
- Inflammation in the joint
- Characteristic joint swelling and stiffness in the morning
- Tenderness over the joint (pain on applying pressure over the joint)
- Symmetric polyarthritis — the same joints are involved on both sides of the body
- Findings of rheumatoid nodules under the skin, commonly over the elbows or fingers
- Joint deformity
Blood tests to diagnose rheumatoid arthritis
Your doctor may arrange blood tests to help confirm the diagnosis. No blood test can definitively be specific and prove or rule out a rheumatoid arthritis diagnosis, but the tests indicated can make the doctor strongly suspect this condition.
Some of the main blood tests used include:
- Erythrocyte Sedimentation Rate (ESR) is raised due to the presence of inflammation caused by rheumatoid arthritis.
- Red blood cell count decreases due to the presence of mild anemia, which is seen in about 33 to 66 percent of all RA patients.
- Platelet count increases due to inflammation. However, it can decrease due to the side effects of drugs.
- C – Reactive proteins (CRP) are raised, again due to inflammation in an active RA. This test also helps to gauge disease activity and response to treatment.
- The rheumatoid factor test also called the RA factor test looks for specific antibodies and measures levels of rheumatoid factors in the blood. Rheumatoid factor is present in about 50 to 80% of RA patients. Higher levels of RA factor indicate higher levels of inflammation.
- Antinuclear antibodies (ANA) are raised in about 40% of RA cases. However, this is not a specific test for RA as ANA can be found raised in other diseases as well.
- Assessment of liver and kidney function is important for treatment options. For example, a patient with kidney insufficiency will not be prescribed a nonsteroidal anti-inflammatory drug (NSAID). Similarly, methotrexate is contraindicated in patients with liver diseases such as hepatitis C and renal impairment.
Imaging studies to diagnose rheumatoid arthritis
- X-rays of the involved joints show loss of bone density and erosion of the cartilage and edges of the bones. On x-ray, this shows as reduced joint space. Inflammation of soft tissues around the joints is also seen. Characteristic periarticular erosive changes may be indicative of a more aggressive rheumatoid arthritis disease.
- MRI is particularly useful in detecting the erosion of cartilage and bones of RA in the early stages.
- Bone densitometry is done to detect osteoporosis, which develops in RA.
In 2010, the American College of Rheumatology and the European League Against Rheumatism jointly created new classification criteria for rheumatoid arthritis. Medscape.com gives a good account of it.