Many medical conditions, including different osteoarthritis and other forms of arthritis, result in physical symptoms such as joint pain and inflammation similar to those seen in early rheumatoid arthritis (RA). To complicate early diagnosis, clinical tests may continue to show normal results for months after physical symptoms first develop. Together, the results of a physical examination, blood tests and other clinical tests, such as specialized X-rays, ultrasound techniques and magnetic resonance imaging (MRI), may indicate rheumatoid arthritis. A physician may use any combination of these tools to make a diagnosis.
Physical Exam
The first step in diagnosis of RA is a physical examination of the joints, wherein a physician invariably hears complaints of pain and stiffness, particularly in the wrists, hands and fingers. The doctor will look for signs of joint weakness, fluid in the joints (indicating inflammation) and fever. The doctor will also ask about the presence and duration of RA symptoms such as morning stiffness and loss of function. If the symptoms are indicative of RA, the doctor will refer you for blood testing. At the same time, or possibly at a later date, you may be referred for clinical tests that involve imaging or scans.
Blood Tests
Several blood tests can be used to help a physician diagnose rheumatoid arthritis. These include a blood test for rheumatoid factor, which indicates the presence of antibodies in the synovium fluid that surrounds the joints.
A physician cannot make a diagnosis based on the presence of rheumatoid factor alone, however, because some people with RA do not have rheumatoid factor in their blood, and some people have rheumatoid factor that may be indicative of another disease. The presence of rheumatoid factor along with other symptoms and positive test results can help a doctor diagnose RA.
Other tests that help a doctor diagnose RA, when other factors are ruled out, include a test for increased C-reactive protein, which also increases with obesity, and a test for anemia, to detect reduced red blood cell count and reduced iron in the blood.
The best combination of blood tests for diagnosing RA is the test for rheumatoid factor and what is known as an anti-CCP antibody test, which is a test for very the presence of very specific antibodies in the blood. When the results of both these tests are positive, a doctor can most successfully diagnose RA and predict its progression.
Clinical Tests
One difference between RA and osteoarthritis is the bone loss due to erosion found in RA. Although difficult to evaluate, early bone loss may be detected by dual energy x-ray absorptionmetry (Dexa scans). When bone loss can be seen in these scans and blood tests reveal elevated rheumatoid factor, a physician can diagnose RA and predict ongoing joint damage. Magnetic resonance imaging (MRI) may also be used to identify this signature bone loss in the hands.
Certain ultrasound techniques can also be used to diagnose RA. Power Doppler ultrasonography (PDUS) can detect inflammation in joints and quantitative ultrasound may pick up bone loss in the fingers.
