Rheumatoid arthritis is an autoimmune disease that can be symptomatic for a few months or a lifetime, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases. Another form of rheumatoid arthritis has occasional symptomatic periods, or flares. Approximately one in every 200 people in the United States has a form of rheumatoid arthritis. Blood tests are used in diagnosis and management of rheumatoid arthritis.
About
Rheumatoid arthritis is an inflammatory disease that affects joints symmetrically. The body forms antibodies against itself, causing the lining of the joints, or synovium, to become red and enlarged. Over time, severe degeneration of joints and tendons occurs. No single test has been found that diagnoses rheumatoid arthritis. Clinical exams, X-rays and abnormal laboratory values are used to make the diagnosis and assess treatment effectiveness.
Rheumatoid Factor
The U.S. Library of Medicine's MedlinePlus website describes rheumatoid factor as an antibody in the body that is also found in other autoimmune diseases. Of those with rheumatoid arthritis, 20 percent will never develop this antibody. Elevated levels of this antibody help diagnose rheumatoid arthritis in some patients, according to Duke University.
Erythrocyte Sedimentation Rate
Erythrocyte sedimentation rate, or ESR, measures how fast red blood cells fall to the bottom of a standardized tube. Duke University lists rheumatoid arthritis, bone infection, leprosy, connective tissue diseases and infection of the heart as conditions that cause the red cells to fall faster, producing an elevated ESR. As listed by MedlinePlus, the normal values are slightly higher for ages over 50 years and for females. ESR is used to monitor inflammation in arthritis, and it should decrease with successful treatment of rheumatoid arthritis.
C-Reactive Protein
Another marker of inflammation is C-reactive protein, or CRP, which is produced by the liver. Cancer, infection, inflammatory bowel disease, lupus and tuberculosis raise CRP. MedlinePlus notes that females on birth control pills and in the last months of pregnancy have elevated CRP values. Most but not all rheumatoid arthritis patients who have flares of the disease show elevated levels during symptomatic periods. Decreases in CRP are evidence of anti-inflammatory medications working in patients with rheumatoid arthritis. One form of CRP, high-sensitivity C-reactive protein, or hs-CRP, is used to measure the risk for heart disease.
Complete Blood Cell Count
In medicine, one of the most often used tests is the complete blood cell count, or CBC. This test measures oxygen-carrying red blood cells; hemoglobin, which is the protein that carries oxygen; infection-fighting white blood cells, and platelets, which are important in blood clotting. In rheumatoid arthritis, inflammation creates an increase in white blood cells. MedlinePlus explains that anemia or a decrease in red blood cells can be seen in rheumatoid arthritis and several other conditions.
Synovial Fluid Analysis
To help determine the cause of joint swelling, a physician may remove some fluid from an inflamed joint for analysis. This test shows bacteria when infection is present or crystals when the joint swelling is caused by gout. Duke University reports the joint fluid in rheumatoid arthritis is less viscous and contains more protein than fluid from normal joints. It should not contain bacteria or crystals.
Genetic
There are several possible genes that have been associated with rheumatoid arthritis. Dr. John Klippel, president of the Arthritis Foundation, describes genetic testing as being in the early stages for rheumatoid arthritis. Most who have genes identified with rheumatoid arthritis don't develop the disease. In 2010, Klippel feels there is little practical value for genetic testing, but it will become important in the future.
In July 2010, attention was focused on a deficiency in sialic acid acetylesterase, or SIAE, having a genetic association with development of autoimmune diseases, including rheumatoid arthritis and diabetes. The National Institute of Arthritis and Musculoskeletal and Skin Diseases reports that 24 of 923 autoimmune disease patients had genetic mutations involving SIAE. At present, there is no single laboratory test to determine who has or will develop rheumatoid arthritis.
References
- Arthritis Foundation: Ask Dr. Klippel: Rheumatologist: Rheumatoid Arthritis
- MedlinePlus: Rheumatoid Arthritis
- Duke University: Wheeless Textbook of Orthopaedics: Laboratory Aspects of RA
- National Institute of Arthritis and Musculoskeletal and Skin Diseases: Rare Gene Variants Associated With Rheumatoid Arthritis, Type 1 Diabetes
