Rheumatoid Arthritis (cont.)
Rheumatoid Arthritis Diagnosis
On hearing your symptoms, your health care professional will suspect that you have rheumatoid arthritis or another type of arthritis or rheumatic disease. The diagnosis doesn't end there though. It is very important to know exactly which type of arthritis you have, because the treatment and outlook for each type can be different.
Your health care professional will conduct a thorough interview and physical examination to try to pinpoint the cause of the symptoms. You will be asked about your symptoms, about other medical problems now and in the past, about your family's medical problems, about the medications you take, and about your habits and lifestyle.
There is no single test to confirm the diagnosis of rheumatoid arthritis. Your health care professional will use the results of your interview and physical examination, lab tests, and imaging studies such as X-rays to determine whether or not you have rheumatoid arthritis. At any time in the process of making the diagnosis or treating the condition, your primary care physician may refer you to a rheumatologist (a specialist in diagnosing and treating rheumatoid arthritis).
Lab tests: Your health care professional may suggest any of the following tests:
- Complete blood count: This test measures how many of each type of blood cell are in your blood. This will show anemia as well as abnormalities in white blood cell counts or platelet counts that can occur with rheumatoid arthritis.
- Markers of inflammation: These include measures such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Levels of both of these are usually elevated in active rheumatoid arthritis and may be good indicators of the extent of disease activity at any given time.
- Other blood tests: Levels of electrolytes (such as calcium, magnesium, and potassium) and proteins may be tested. Kidney and liver functions also may be checked and monitored while taking medications.
- Immunologic tests: Blood levels of rheumatoid factor (RF), antinuclear antibodies (ANA), and possibly other antibodies (anti-citrulline antibody or anti-CCP) may be checked. The majority of people have a positive RF result during periods of active disease. A positive ANA result
can indicate an unusually active immune system. About 40% of people with rheumatoid arthritis have a positive ANA result. In the first few months of onset of rheumatoid arthritis, these immunologic tests may be negative, and, in some patients, they are always negative.
Synovial fluid analysis: The tissue that lines the joint (synovium) produces fluid that helps lubricate and protect joints. Like blood, this fluid may be abnormal in quality and excessive quantity from rheumatoid arthritis. It may reveal characteristic signs of inflammation that point to rheumatoid arthritis, such as an elevated number of white blood cells. A sample of this fluid is withdrawn from a joint (usually the knee) through a needle in a procedure called arthrocentesis, or joint aspiration. The fluid is examined and analyzed for signs of inflammation.
Imaging studies: X-rays and sometimes other imaging studies often are used to detect damage to the joints.
- X-rays: X-rays may be taken of sites where symptoms or signs occur. Early in rheumatoid arthritis, the
X-ray may be normal or show only soft-tissue swelling, but damage can still be occurring. Over time, the usual finding is erosion of the bony part of the joint. Bone erosion occurs in nearly 80% of patients with one year of untreated disease. These changes are distinguishable from changes seen with other types of arthritis such as osteoarthritis.
- MRI: Magnetic resonance imaging (MRI) may allow earlier detection of bone erosion than plain film X-rays.
- Ultrasound: Ultrasound uses high-frequency sound waves to produce images of structures inside the body. It can be used to examine and to detect abnormal collections of fluid in the soft tissues around joints. The abnormal collection of joint fluid is referred to as a joint effusion.
- Bone scanning: In this test, a special image of the entire skeleton is obtained after a small amount of radioactive isotope is injected into a vein. Diseased or damaged bone takes up the radioisotope in a different way than healthy bone and produces a characteristic picture on
X-ray films. This technique may be used to detect inflammatory changes in bone.
- Densitometry: This scan detects
decreases in the thickness of bone that may indicate osteoporosis. Osteoporosis occurs more frequently in patients with rheumatoid arthritis.
- Arthroscopy: In this
test, a small scope, a long narrow tube with a light and a camera on the end, is used to examine the inside of the joint. The scope is inserted through a small incision in the skin. The camera transmits pictures to a video monitor, allowing the doctor to detect signs of rheumatoid arthritis or other joint disease. This test is not always necessary.
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