Approach

Diagnosis is predominantly based on clinical manifestations. Patients with suspected JIA should be referred promptly to a paediatric rheumatologist for further evaluation.

History

Clinicians should elicit the following information:

  • Current joint symptoms (e.g., pain, swelling, morning stiffness)

  • Which joints are affected

  • Whether symptoms are symmetrical or asymmetrical

  • Presence of gait abnormality

  • Diurnal variation in symptoms

  • Presence of fever

  • Presence of skin change (rashes, easy bruising)

  • Any history of mouth ulcers

  • Any history of intercurrent infection, trauma, weight loss, or night sweats

  • Any ocular symptoms suggestive of uveitis (although uveitis is often asymptomatic in patients with JIA)

  • Family history of JIA, psoriasis, or autoimmunity.

Physical examination

Initial observations may reveal pyrexia, and general inspection may reveal macular rashes, psoriatic scales, purpura, or bruising. Nail changes and/or dactylitis may also be evident. Examination of affected limbs may demonstrate symmetrical or asymmetrical oedematous and/or tender joints, and gait assessment may show limping.

Laboratory tests

Once clinical diagnosis is made, laboratory tests support subtype classification. They can guide monitoring and treatment and help determine prognosis. Full blood count is normal in most subtypes except systemic-onset juvenile idiopathic arthritis. Erythrocyte sedimentation rate (ESR) and/or C-reactive protein are often performed and may be elevated to varying levels dependent on JIA subtype. ESR is a component of the juvenile arthritis disease activity score, which informs choice of initial treatment.[46]

Antinuclear antibodies (ANA) are detected in 30% to 60% of children.[47][48][49] ANA positivity is a risk factor for the development of uveitis, so this test is routinely performed at diagnosis. Rheumatoid factor is positive in about 2% to 7% of children with JIA (usually older children with polyarticular JIA).[50]

A Chlamydia screen may be indicated in teenage patients with monoarticular disease.

Imaging

Radiographic investigations can aid diagnosis but are not specific, and results (particularly from x-rays) may be normal during early stages of disease.

Magnetic resonance imaging (MRI) and ultrasound can provide information about joints that are difficult to examine (including hips, temporomandibular joints, small joints of the feet, etc.).[51] Ultrasound examination of the joints has demonstrated higher sensitivity in assessing synovitis than clinical examination. However, further studies are needed to evaluate the reliability and responsiveness of ultrasound in assessing synovitis changes on follow-up.[52] Subclinical synovitis can be detected by ultrasound and as a result this can be useful at diagnosis and throughout the disease course.[53][54]

MRI is of particular value in assessing disease activity in patients with long-standing disease and can be used to assess response to treatment.[55] MRI is also helpful in excluding other diagnoses, such as pigmented villonodular synovitis or effusions in joints where effusions are hard to detect clinically or by plain x-ray (e.g., hips). When MRI is indicated, it should be performed with gadolinium, which demonstrates synovial enhancement.

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