Diagnosis
Doctors may order a blood test for the genetic factor HLA-B27, but a positive result does not always mean that a person has the disorder.
Doctors may order other blood tests to help rule out other conditions and confirm diagnosis. Rheumatoid factor or antinuclear antibody tests can help rule out reactive arthritis. Most who have reactive arthritis will have negative results on these tests. If the test results are positive, you may have some other type of arthritis, such as:
Doctors may also test for erythrocyte sedimentation rate. A high "sed rate" often indicates inflammation somewhere in the body. Typically, people with rheumatic diseases have an elevated sed rate.
Infections
Doctors likely will test for infections that might be associated with reactive arthritis. Patients generally are tested for a Chlamydia infection (studies have shown that early treatment of Chlamydia-induced reactive arthritis may reduce disease progression). Cell samples may be taken from the throat, urethra in men or cervix in women. Urine and stool samples also may be tested. A sample of synovial fluid may be removed from the arthritic joint. Studies of synovial fluid can help rule out infection in the joint.
X Rays
Doctors sometimes use x ray to help diagnose reactive arthritis and to rule out other causes of arthritis. X rays can detect other symptoms including:
- spondylitis
- sacroiliitis
- soft tissue swelling
- damage to cartilage and joints
- calcium deposits
