Material provided by the National Institute of Arthritis and Musculoskeletal and Skin Diseases. You may visit their website at www.nih.com.

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Doctors usually suspectu juvenile idiopathic arthritis (JIA), along with several other possible conditions, when they see children with persistent joint pain or swelling, unexplained skin rashes and fever, or swelling of lymph nodes or inflammation of internal organs. A diagnosis of JIA also is considered in children with an unexplained limp or excessive clumsiness.

No one test can be used to diagnose JIA. A doctor diagnoses JIA by carefully examining the patient and considering the patient's medical history and the results of laboratory tests that help rule out other conditions.

Pay Attention to the Symptoms
One important consideration in diagnosing JIA is the length of time that symptoms have been present. Joint swelling or pain must last for at least 6 weeks for the doctor to consider a diagnosis of JIA. Because this factor is so important, it may be useful to keep a record of the symptoms, when they first appeared, and when they are worse or better.

Lab Tests
Lab tests, usually blood tests, cannot by themselves provide the doctor with a clear diagnosis. But these tests can be used to help rule out other conditions and to help classify the type of JIA that a patient has. Blood may be taken to test for the rheumatoid factor (RF) and / or for anti-nuclear anti-bodies (ANA). Blood tests may also be done to determine the erythrocyte sedimentation rate (ESR).

The presence of ANA and / or RF in the blood can indicate juvenile idiopathic arthritis. ANA is found in the blood more often than RF, and both are found in only a small portion of JIA patients. Therefore, the presence of ANA and / or RF does not guarantee the presence of JIA.

The RF test specifically helps the doctor tell the difference among the three types of JIA.

ESR is a test that measures how quickly red blood cells fall to the bottom of a test tube. Some people with rheumatic disease have an elevated ESR or "sed rate" (cells fall quickly to the bottom of the test tube), showing that there is inflammation in the body. Not all children with active joint inflammation have an elevated ESR.

X-rays
X-rays are needed if the doctor suspects injury to the bone or unusual bone development. Early in the disease, some x-rays can show cartilage damage. In general, x-rays are more useful later in the disease, when bones may be affected.

 Other Diseases
Because there are many causes of joint pain and swelling, the doctor must rule out other conditions before diagnosing JIA. These include physical injury, bacterial infection, Lyme disease, inflammatory bowel disease, lupus, dermatomyositis, and some forms of cancer. The doctor may use additional laboratory tests to help rule out these and other possible conditions.

Note: Juvenile idiopathic arthritis (JIA) was previously known as Juvenile rheumatoid arthritis (JRA).