Investigations

• The approach to investigations must always focus on making an accurate diagnosis, planning management or monitoring of the disease. 
• Laboratory tests are used to support or exclude potential diagnoses. They can also be used to monitor progress, response to treatment or adverse side effects of medication. 
• If pathology such as inflammatory arthritis is suspected, blood tests and radiographs can be normal. Referral early to paediatric rheumatology is advised if there is clinical concern. 
• Taking blood from children can be traumatic so it is important to make sure that venepuncture is done by experienced staff. Tests must always be justified and the minimum amount of blood taken. Knowing normal values is helpful in the interpretation of tests. 
• Imaging is useful but may need sedation in young children. It is important to plan investigations to gain the most information and minimise radiation exposure or need for sedation.
• Radiographs or Computerised Tomography (CT) result in radiation exposure. 
• Ultrasound scanning is increasingly used, does not result in radiation exposure and does not require sedation.
• Magnetic Resonance Imaging (MRI) may need sedation.
• Children may need analgesia to enable assessment to take place and during investigations. 
• Rheumatoid factor is usually negative in children with arthritis. 
• Antinuclear antibody (ANA) is often found in normal healthy children. ANA is not diagnostic of JIA or any other disease.