What is the workup for juvenile idiopathic rheumatoid arthritis (JIA)?

Workup for Juvenile Idiopathic Arthritis

The workup for JIA requires establishing arthritis persisting ≥6 weeks in a child <16 years old, excluding other known conditions through targeted laboratory testing, imaging to assess joint involvement and damage, and ophthalmologic screening for uveitis. 1

Clinical Assessment

History and Physical Examination

• Document joint involvement pattern: Count and record all joints with swelling, tenderness, warmth, or limited range of motion to classify disease subtype (oligoarticular <5 joints vs polyarticular ≥5 joints) 1
• Assess for systemic features: Recurrent fever, characteristic salmon-pink rash, hepatosplenomegaly, lymphadenopathy, and serositis suggest systemic JIA 2
• Identify enthesitis: Examine tendon insertion sites (Achilles, patellar tendon, plantar fascia) for tenderness and swelling, particularly in lower extremities 3
• Evaluate for extra-articular manifestations: Morning stiffness duration, growth disturbances, functional limitations in daily activities 2, 4

Laboratory Testing

Essential Initial Tests

• Complete blood count: Assess for anemia of chronic disease, thrombocytosis (systemic JIA), leukocytosis 2
• Inflammatory markers: ESR and CRP to quantify inflammation, though normal values do not exclude JIA 2
• Rheumatoid factor (RF): Positive in <10% of JIA patients; when positive (especially if persistent), defines RF-positive polyarticular subtype with worse prognosis 3, 2
• Anti-cyclic citrullinated peptide (anti-CCP) antibodies: Identifies patients at higher risk for erosive disease and poor outcomes 3
• Antinuclear antibodies (ANA): Positive in 40-85% of oligoarticular JIA; strong predictor of chronic anterior uveitis risk requiring more frequent ophthalmologic screening 2
• HLA-B27: Consider in patients with enthesitis, asymmetric lower extremity arthritis, or sacroiliitis to identify enthesitis-related arthritis subtype 2

Tests to Exclude Other Conditions

• Infectious workup: Consider Lyme serology (endemic areas), throat culture/ASO titers (post-streptococcal arthritis), viral serologies if clinically indicated 4
• Metabolic screening: Uric acid if gout suspected (rare in children), ferritin if systemic JIA or macrophage activation syndrome suspected 2

Imaging Studies

Plain Radiography

• Baseline radiographs of affected joints: Document soft tissue swelling, periarticular osteopenia, joint space narrowing, erosions, and growth disturbances 5
• The American College of Rheumatology recommends specific imaging protocols though evidence quality is low; plain films remain the basic diagnostic and follow-up tool 3, 5
• Cervical spine radiographs: Consider in polyarticular disease to assess for atlantoaxial instability 5

Advanced Imaging

• MRI for sacroiliitis: Required to diagnose active sacroiliitis when clinical examination suggests inflammatory back pain or sacroiliac joint tenderness 3
• Ultrasound: Can detect synovitis, effusions, and guide intra-articular injections, though not specifically addressed in recent ACR guidelines 3

Ophthalmologic Evaluation

• Mandatory slit-lamp examination: All JIA patients require screening for chronic anterior uveitis, which is often asymptomatic initially 2
• Screening frequency based on risk: ANA-positive oligoarticular JIA patients (highest risk) require more frequent examinations than other subtypes 2

Disease Activity Assessment

• Calculate cJADAS-10 score: Clinical Juvenile Disease Activity Score based on 10 joints; low disease activity defined as ≤2.5 with ≥1 active joint, moderate/high activity >2.5 3, 1
• Document functional status: Use validated tools to assess impact on daily activities and quality of life 3

Common Pitfalls to Avoid

• Do not delay workup waiting for RF positivity: RF is negative in >90% of JIA patients; diagnosis is clinical with supportive laboratory findings 2
• Do not miss uveitis screening: Chronic anterior uveitis can cause permanent vision loss and is often asymptomatic; regular ophthalmologic follow-up is mandatory 2
• Do not overlook systemic JIA complications: Monitor for macrophage activation syndrome (ferritin >10,000 ng/mL, cytopenias, coagulopathy, hepatosplenomegaly) which is life-threatening 2, 4
• Do not assume normal inflammatory markers exclude JIA: Some patients, particularly those with oligoarticular disease, may have normal ESR/CRP 2

Monitoring Recommendations

The American College of Rheumatology recommends specific laboratory monitoring schedules for medications, though the workup itself focuses on establishing diagnosis and baseline assessment 3