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Physical Examination
Physical examination is one of the initial rheumatoid arthritis diagnostic tests performed by doctors. During a physical exam, doctors carefully feel and examine the joints for signs of swelling and tenderness which are classic symptoms of RA. They also look for other symptoms like joint stiffness that lasts for more than 30 minutes after waking up or after periods of inactivity. Abnormal range of motion in joints due to joint destruction is also noted. The symmetrical involvement of small joints in hands and feet is an important clue for the diagnosis of rheumatoid arthritis.
Blood Tests
A variety of blood tests are ordered as part of the initial rheumatoid arthritis workup. These blood tests help to determine inflammation and confirm the diagnosis.
Rheumatoid Factor (RF) Test
The rheumatoid factor (RF) test is designed to detect elevated levels of rheumatoid factor, which is an antibody often present in people with rheumatoid arthritis. Approximately 80% of people with established rheumatoid arthritis will test positive for RF. However, RF can also be present at lower levels in some other autoimmune diseases and even healthy individuals. A positive RF result increases the likelihood of a rheumatoid arthritis diagnosis but a negative RF does not rule it out.
C-Reactive Protein (CRP) Test
The c-reactive protein (CRP) blood test measures levels of CRP, a protein produced by the liver during systemic inflammation. Elevated CRP levels are commonly seen during rheumatoid arthritis flares and periods of active disease. CRP is not specific to rheumatoid arthritis and can also be elevated during other inflammatory conditions. Doctors may use CRP results along with other tests to monitor rheumatoid arthritis disease activity over time.
Erythrocyte Sedimentation Rate (ESR) Test
The erythrocyte sedimentation rate (ESR) test indirectly measures inflammation in the body by tracking how fast red blood cells settle in a tube of blood over a period of one hour. An elevated ESR often accompanies active rheumatoid arthritis. Similarly to CRP, an increased ESR is non-specific and could be associated with other inflammatory diseases as well. ESR may be used in conjunction with other tests to determine rheumatoid arthritis disease activity.
Anti-CCP Antibody Test
The anti-CCP (cyclic citrullinated peptide) antibody blood test directly detects antibodies against a protein called citrullinated protein/peptide. The presence of anti-CCP antibodies is highly specific for rheumatoid arthritis. Approximately 70% of people with rheumatoid arthritis will test positive for anti-CCP antibodies. A positive anti-CCP result adds significant diagnostic value beyond RF testing alone.
Joint Aspiration and Synovial Fluid Analysis
If a joint appears swollen or inflamed based on physical examination, doctors may perform a joint aspiration procedure. Using a thin needle, fluid is extracted from the joint space. Synovial fluid analysis can identify signs of inflammation like increased white blood cell count that are characteristic of inflammatory arthritis like rheumatoid arthritis. The fluid can also be tested for presence of rheumatoid factor for additional confirmation. Synovial fluid analysis provides supportive evidence for confirming a clinical suspicion of rheumatoid arthritis.
X-Rays
Plain x-rays of affected joints are commonly ordered as part of the rheumatoid arthritis evaluation. Early x-ray findings may include soft tissue swelling around joints. Later changes typically involve joint damage seen as erosions on x-ray images of the bones adjacent to joints. Loss of bone density, narrowed joint spaces, and deformities like subluxations are also appreciated on x-rays as rheumatoid arthritis progresses if left untreated. X-ray findings become evident later than clinical or laboratory abnormalities after the onset of symptoms. Nevertheless, x-rays are useful for documenting rheumatoid arthritis damage over time.
Ultrasound Imaging
Musculoskeletal ultrasound allows doctors to visualize soft tissues like tendons, ligaments, and joint recesses in real time. Ultrasound is very useful for detecting early rheumatoid arthritis findings in joints. Abnormalities seen on ultrasound may precede x-ray changes and include synovial hypertrophy, joint effusions, and tiny bone erosions. Since it does not use ionizing radiation like x-rays, ultrasound is well-suited to serially monitor joint inflammation and structural changes in rheumatoid arthritis patients over the long term.
MRI Scans
Magnetic resonance imaging or MRI provides very high-resolution images of bones and soft tissues and has become an important imaging modality for rheumatoid arthritis. MRI is more sensitive than ultrasound or x-rays for identifying early rheumatoid arthritis changes in the joints. Characteristic findings are synovitis, bone marrow edema, and tiny erosions seen as areas of brightness on MRI. Whole-body MRI provides an unparalleled view of the extent and distribution of rheumatoid arthritis pathology. It helps guide doctors regarding the most problematic joints to treat. MRI plays a role in diagnosis and can predict future joint damage in rheumatoid arthritis.
While rheumatoid arthritis remains a clinical diagnosis based on symptoms, physical exam findings, and appropriate test results, the above described diagnostic testing helps decrease diagnostic uncertainty and accurately confirm the presence of rheumatoid arthritis as the underlying cause of joint symptoms. An integrated approach including physical examination, laboratory tests, and imaging studies provides doctors with important information needed to definitively diagnose the condition and guide the best treatment plan.
