DIAGNOSES OF ARTHRITIS

How is rheumatoid arthritis diagnosed?

There is no singular test for diagnosing rheumatoid arthritis. Instead, rheumatoid arthritis is diagnosed based on a combination of the presentation of the joints involved, characteristic joint stiffness in the morning, the presence of blood rheumatoid factor and citrulline antibody, as well as findings of rheumatoid nodules and radiographic changes (X-ray testing).
The first step in the diagnosis of rheumatoid arthritis is a meeting between the doctor and the patient. The doctor reviews the history of symptoms, examines the joints for inflammation, tenderness, swelling, and deformity, the skin for rheumatoid nodules (firm bumps under the skin, most commonly over the elbows or fingers), and other parts of the body for inflammation. Certain blood and X-ray tests are often obtained. The diagnosis will be based on the pattern of symptoms, the distribution of the inflamed joints, and the blood and X-ray findings. Several visits may be necessary before the doctor can be certain of the diagnosis. A doctor with special training in arthritis and related diseases is called a rheumatologist.
The distribution of joint inflammation is important to the doctor in making a diagnosis. In rheumatoid arthritis, the small joints of the hands, wrists, feet, and knees are typically inflamed in a symmetrical distribution (affecting both sides of the body). When only one or two joints are inflamed, the diagnosis of rheumatoid arthritis becomes more difficult. The doctor may then perform other tests to exclude arthritis due to infection or gout. The detection of rheumatoid nodules (described above), most often around the elbows and fingers, can suggest the diagnosis.
Abnormal antibodies can be found in the blood of people with rheumatoid arthritis. An antibody called "rheumatoid factor" can be found in 80% of patients with rheumatoid arthritis. Patients who are felt to have rheumatoid arthritis and do not have positive rheumatoid factor testing are referred as having "seronegative rheumatoid arthritis." Citrulline antibody (also referred to as anticitrulline antibody, anticyclic citrullinated peptide antibody, and anti-CCP) is present in most people with rheumatoid arthritis. It is useful in the diagnosis of rheumatoid arthritis when evaluating cases of unexplained joint inflammation. A test for citrulline antibodies is most helpful in looking for the cause of previously undiagnosed inflammatory arthritis when the traditional blood test for rheumatoid arthritis, rheumatoid factor, is not present. Citrulline antibodies have been felt to represent the earlier stages of rheumatoid arthritis in this setting. Another antibody called the "antinuclear antibody" (ANA) is also frequently found in people with rheumatoid arthritis.
A blood test called the sedimentation rate (sed rate) is a measure of how fast red blood cells fall to the bottom of a test tube. The sed rate is used as a crude measure of the inflammation of the joints. The sed rate is usually faster during disease flares and slower during remissions. Another blood test that is used to measure the degree of inflammation present in the body is the C-reactive protein. Blood testing may also reveal anemia, since anemia is common in rheumatoid arthritis, particularly because of the chronic inflammation.
The rheumatoid factor, ANA, sed rate, and C-reactive protein tests can also be abnormal in other systemic autoimmune and inflammatory conditions. Therefore, abnormalities in these blood tests alone are not sufficient for a firm diagnosis of rheumatoid arthritis.
Joint X-rays may be normal or only show swelling of soft tissues early in the disease. As the disease progresses, X-rays can show bony erosions typical of rheumatoid arthritis in the joints. Joint X-rays can also be helpful in monitoring the progression of disease and joint damage over time. Bone scanning, a procedure using a small amount of a radioactive substance, can also be used to demonstrate the inflamed joints. MRI scanning can also be used to demonstrate joint damage.
The American College of Rheumatology has developed a system for classifying rheumatoid arthritis that is primarily based upon the X-ray appearance of the joints. This system helps medical professionals classify the severity of your rheumatoid arthritis with respect to cartilage, ligaments, and bone.
Stage I

• no damage seen on X-rays, although there may be signs of bone thinning

Stage II

• on X-ray, evidence of bone thinning around a joint with or without slight bone damage
• slight cartilage damage possible
• joint mobility may be limited; no joint deformities observed
• atrophy of adjacent muscle
• abnormalities of soft tissue around joint possible

Stage III

• on X-ray, evidence of cartilage and bone damage and bone thinning around the joint
• joint deformity without permanent stiffening or fixation of the joint
• extensive muscle atrophy
• abnormalities of soft tissue around joint possible

Stage IV

• on X-ray, evidence of cartilage and bone damage and osteoporosis around joint
• joint deformity with permanent fixation of the joint (referred to as ankylosis)
• extensive muscle atrophy
• abnormalities of soft tissue around joint possible

Rheumatologists also classify the functional status of people with rheumatoid arthritis as follows:

• Class I: completely able to perform usual activities of daily living
• Class II: able to perform usual self-care and work activities but limited in activities outside of work (such as playing sports, household chores)
• Class III: able to perform usual self-care activities but limited in work and other activities
• Class IV: limited in ability to perform usual self-care, work, and other activities

The doctor may elect to perform an office procedure called arthrocentesis. In this procedure, a sterile needle and syringe are used to drain joint fluid out of the joint for study in the laboratory. Analysis of the joint fluid in the laboratory can help to exclude other causes of arthritis, such as infection and gout. Arthrocentesis can also be helpful in relieving joint swelling and pain. Occasionally, cortisone medications are injected into the joint during the arthrocentesis in order to rapidly relieve joint inflammation and further reduce symptoms.