Juvenile rheumatoid arthritis (JRA) may be difficult to diagnose. Many children may not experience identifiable symptoms, or the symptoms they do have may be caused by other conditions, such as lupus, Lyme disease or bone disorders.

The first sign is usually a complaint of joint pain or swelling by the child, or sometimes a limp noticed by parents. A diagnostic visit for JRA can be conducted by a pediatrician. A pediatrician who suspects JRA may refer the case to a pediatric rheumatologist, a physician who specializes in arthritis and other inflammatory diseases in children.

A physical examination includes checking the joints for swelling, warmth, tenderness and range of motion. The physician notes descriptions and incidences of pain and its duration. The physician may try to move various joints to see if motion causes pain. The diagnosis will also include a medical history, including any family history of arthritis or autoimmune conditions, previous injuries or surgeries and general use of the joints. The physician will also note any fevers, rashes or infections.

Many laboratory tests are used to screen for specific kinds of arthritis or other diseases. Certain blood tests may produce characteristic results for some types of JRA, and thus may be used to classify which type of JRA is present. None of these tests definitively diagnose JRA. The blood tests include:

• Complete blood count (CBC). Measures the levels of different types of blood cells. Children with JRA may show a low count of red blood cells (anemia) and elevated counts of white blood cells.
  
  
• Erythrocyte sedimentation rate (ESR or sed rate). If elevated, indicates inflammation but not its cause. It is always elevated for systemic and polyarticular JRA but may be within the normal range for children with pauciarticular JRA.
  
  
• Antinuclear antibody (ANA) test. Tests for certain autoimmune disorders such as lupus. Not all children with JRA have this antibody. Those who test positive for ANA are more likely to develop eye inflammations such as uveitis. Children with systemic JRA usually test negative for ANA. This antibody is found positive in 75 to 85 percent of cases of pauciarticular JRA, 40 to 50 percent of cases of polyarticular JRA and about 10 percent of cases of systemic JRA.
  
  
• Rheumatoid factor test. Identifies the presence of the rheumatoid factor (RF) antibody. Children with systemic JRA usually test negative for rheumatoid factor. Some children with polyarticular JRA test positive for RF. RF testing thus helps differentiate among the three types of JRA.

Another test that may be used for JRA is a synovial fluid analysis. Fluid from an affected joint is withdrawn with a needle (a procedure called arthrocentesis). Examining this fluid may help determine if the inflammation is caused by JRA or some other condition. Arthrocentesis is also used to diagnose any joint infection.

A diagnostic examination where JRA is suspected may also include x-rays. Images are taken of the affected joints and may help rule out other potential causes. Additional tests may also be used to rule out other potential bone problems, such as congenital deformities or bone cancer. These include CAT scans (computed axial tomography), where multiple x-ray images are taken, bone scans, which can show bone inflammation not evident on x-ray, and MRI (magnetic resonance imaging), which uses powerful magnets to form an image of the bone and tissues.

When JRA is suspected, a pediatrician will also refer the patient to an ophthalmologist, a physician who specializes in eye diseases. Children with JRA are susceptible to eye inflammations, which may not exhibit symptoms. The ophthalmologist may perform an examination with a device called a slit lamp, which has high-intensity light that can be focused in a narrow area. It is used to examine some of the structures of the eye such as the iris and other parts of the uveal tract (middle eye) that are subject to inflammation. Children with JRA should receive eye examinations by an ophthalmologist regularly.