An evaluation of adult Still's disease begins with a medical history and physical examination.

Physical findings in those with adult Still's disease may include:

• Decreased mobility of the joints
• Joint redness
• Joint tenderness
• Joint swelling
• Joint warmth
• Heart murmur

Tests are required for the diagnosis of adult Still's disease.

Blood tests that may be performed in the evaluation adult Still's disease include:

• ANA titers:
• Positive in 20-30%
• Anti-microsomal antibodies
• Anti-mitochondrial antibodies
• Antistreptolysin-O titer
• Complement titers
• Complete blood count
• Erythrocyte sedimentation rate
• HLA-B27
• Liver profile
• Kidney profile
• Rheumatoid factor: positive in 70-80%
• Thyroglobulin antibodies

Other tests used to determine the severity of arthritis in adult Still's disease include:

• Arthrocentesis:
• Analysis of synovial fluid
• Bone x-rays:
• May be normal in early stages
• Advanced changes of arthritis
• Bone scan
• MRI scanning: may be necessary when clear soft tissue images are important