Juvenile Rheumatoid Arthritis (cont.)

Exams and Tests

It is important to remember that many conditions other than juvenile rheumatoid arthritis can cause joint pain, stiffness, and swelling.

• Examples are infections with bacteria or viruses, injury (such as a sprain or fracture), systemic lupus erythematosus, inflammatory bowel disease, Lyme disease, and certain kinds of cancer.
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• Other symptoms of JRA are similarly not specific, meaning that they can be caused by many different conditions. Fever, for example, is a very common symptom of infection.
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• A child who has joint symptoms needs a thorough evaluation by a qualified medical professional. This evaluation will focus on consideration of many conditions and thus arriving at a specific diagnosis.
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• In some children, the symptoms strongly suggest some type of arthritis. In others, the symptoms and signs are more subtle and require careful investigation by the health care provider. Often, a specialist such as a pediatric rheumatologist is consulted to help with the diagnosis.
  
  

The medical interview is a crucial part of making a diagnosis. You will be asked about the following information. It is important that you answer as completely as possible, as this information may help your child.

• Your child’s symptoms and behavior
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• The child’s other medical problems, injuries, and accidents, either recent or in the past
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• His or her vaccinations, medications, and allergies
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• His or her activities, such as sports and games
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• Family medical history (medical problems in the brothers and sisters, mother and father, and their families)
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• The family’s habits and lifestyle
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• The child’s exposures to pets and other animals
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• Recent travel or time spent outdoors, such as camping, hiking, or on a farm
  
  

A detailed physical examination is another critical tool in the evaluation. The examination will include observing, touching, and moving the joints. Muscle strength and flexibility also will be checked. The person conducting the examination looks specifically for evidence of pain, stiffness, swelling, or deformity. The physical examination will cover all systems of the body, with special focus on systems often affected by JRA, such as the eyes, the skin, the heart, and the digestive tract.

Lab tests

There is no lab test that definitely confirms that a child has JRA. The diagnosis is made from a combination of the information gained from the medical interview and physical examination, from a number of different lab tests, and, in some cases, from x-rays and related tests. Because the symptoms must persist at least 6 weeks to be considered JRA, these lab tests may need to be repeated to confirm the diagnosis. After JRA is diagnosed, the tests are done every so often to check disease activity and the success of treatment. All of these are blood tests unless stated otherwise.

• Erythrocyte sedimentation rate (ESR): ESR is a “nonspecific” marker. It does not point specifically to JRA but indicates active inflammation in the body. It is almost always elevated in children with systemic JRA. It usually is elevated in children with polyarticular disease, but is often normal in those with pauciarticular disease.
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• Complete blood cell count (CBC): This test measures the amounts of each type of blood cell in a sample of blood. It also indicates the level of hemoglobin, the protein in blood that carries oxygen around the body. A low level of hemoglobin, called anemia, is common in children with JRA. This test highlights abnormalities in the numbers of various kinds of white blood cells (part of the immune system) or of platelets (which help blood clot). It can be used to distinguish JRA from other conditions that might have similar symptoms. The white blood cell count and platelet count are usually normal in people with JRA.
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• Antinuclear antibody (ANA): Antinuclear antibody is just one of the antibodies that the body may produce in certain autoimmune diseases (called autoantibodies). As many as 25% of children with JRA have a positive ANA result. A positive ANA result is most common in children with pauciarticular disease. It is uncommon in children with systemic JRA. It is linked to an increased risk of eye involvement (uveitis). ANA is also more likely to be positive in conditions related to JRA (such as SLE or scleroderma) than in JRA. It is often used to rule out these conditions in a person with arthritis symptoms. Very high levels of ANA may increase the risk that the disease will progress to adult-type SLE. 
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• Rheumatoid factor (RF): Rheumatoid factor is actually a group of autoantibodies that occur in some people with RA, JRA, and related conditions. It is most often positive in children with polyarticular JRA and is rarely positive in children with systemic JRA. It is most often used to help determine which type of JRA a child has. Adolescents are more likely to have a positive RF result than younger children. In fact, many consider a positive RF result a sign of JRA progressing to adult-type RA.
  

Imaging studies

Your child’s health care provider may order x-rays or similar imaging studies. These images may help confirm the diagnosis or JRA or suggest other conditions that might cause similar symptoms.

• X-rays: X-rays give information about whether or not damage has occurred in the joint.
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• Bone scan: A bone scan may be necessary if the results of the workup do not support the diagnosis of JRA. A bone scan can detect inflammation in the bone and other abnormalities that do not show up well on x-ray.
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• MRI: MRI is similar to x-ray but is much more detailed and gives a better 3-dimensional view of the joint. It is especially useful if there has been a fall or accident that might have injured joints. It usually is not ordered unless the results of the workup do not point clearly to a diagnosis of JRA.
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• CT scan: CT scan also is similar to x-ray but provides much greater detail. It may be ordered when the results of the workup do not support the diagnosis of JRA. CT scan is particularly good at ruling out tumors and other bony abnormalities that could cause arthritis-like symptoms.
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• Dual-energy x-ray absorptiometry (DEXA) scan: DEXA scanning is used to measure bone density and can identify osteopenia or osteoporosis (loss of bone tissue) in children with polyarticular JRA.
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Other tests

Other tests may be ordered in specific circumstances. Most children with JRA do not require these tests.

• Arthrocentesis: This is sometimes called “joint aspiration.” It means the removal of a sample of synovial fluid (fluid from a joint cavity) for testing. It is usually done to rule out infections in the joints.
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• Synovial biopsy: An orthopedic surgeon uses a probe to remove a small amount of the synovial tissue from a joint. The tissue is examined under a microscope for clues as to what is causing synovial damage. This may be helpful to exclude other conditions that can cause symptoms similar to those of JRA.