What laboratory tests are recommended for the diagnosis and management of Juvenile Idiopathic Arthritis (JIA)?

Laboratory Tests for Juvenile Idiopathic Arthritis (JIA)

For diagnosis and monitoring of JIA, complete blood count (CBC), liver function tests (LFTs), and renal function tests are strongly recommended as the core laboratory tests, with frequency determined by medication regimen and disease activity. 1

Diagnostic Laboratory Tests

Initial Evaluation

• Complete Blood Count (CBC) with differential

  • Evaluates for anemia, leukocytosis, thrombocytosis which may indicate disease activity 2, 3
  • Elevated white blood cell count and platelet count are associated with active disease 3

• Inflammatory Markers

  • Erythrocyte Sedimentation Rate (ESR)
  • C-Reactive Protein (CRP)
  • Note: These may remain elevated even in clinically inactive disease 2

• Autoantibody Testing

  • Rheumatoid Factor (RF) - helps classify JIA subtypes (RF-positive vs RF-negative polyarthritis)
  • Anti-Cyclic Citrullinated Peptide (anti-CCP) antibodies - associated with erosive disease 4
  • Antinuclear Antibodies (ANA) - particularly important in oligoarticular JIA

• Serum Ferritin

  • Particularly important in systemic JIA where levels can be markedly elevated (750-7712 ng/ml) 2

Medication Monitoring

NSAIDs

• CBC, LFTs, and renal function tests every 6-12 months (conditional recommendation) 1

Methotrexate

• CBC, LFTs, and renal function tests:
  • Within first 1-2 months of initiation
  • Every 3-4 months thereafter
  • Strong recommendation 1
• Dose adjustment: Decrease or hold methotrexate if clinically relevant elevation in LFTs or decreased neutrophil/platelet count occurs 1

Sulfasalazine

• CBC, LFTs, and renal function tests:
  • Within first 1-2 months of initiation
  • Every 3-4 months thereafter
  • Conditional recommendation 1
• Dose adjustment: Decrease or hold sulfasalazine if clinically relevant elevation in LFTs or decreased neutrophil/platelet count occurs 1

Leflunomide

• CBC and LFTs:
  • Within first 1-2 months of initiation
  • Every 3-4 months thereafter
  • Conditional recommendation 1
• Dose adjustment: Temporarily hold leflunomide if ALT >3× upper limit of normal (ULN) 1

Hydroxychloroquine

• CBC and LFTs annually (conditional recommendation) 1
• Baseline and annual retinal screening (conditional recommendation) 1

TNF Inhibitors

• CBC and LFTs annually (conditional recommendation) 1
• TB screening prior to initiation and when there is concern for TB exposure thereafter 1

Abatacept

• No routine laboratory monitoring is conditionally recommended 1

Tocilizumab

• CBC and LFTs:
  • Within first 1-2 months of initiation
  • Every 3-4 months thereafter
  • Conditional recommendation 1
• Lipid levels every 6 months (conditional recommendation) 1
• Dose adjustment: Alter administration if monitoring reveals:
  • Elevated LFTs (1-3× ULN: decrease dose/interval; >3× ULN: hold dose; >5× ULN: discontinue)
  • Neutropenia (500-1000/mm³)
  • Thrombocytopenia (50,000-100,000/mm³) 1

IL-1 Inhibitors (Anakinra, Canakinumab)

• CBC and LFTs:
  • Within first 1-2 months of initiation
  • Every 3-4 months thereafter
  • Conditional recommendation 1

Tofacitinib

• CBC and LFTs:
  • Within first 1-2 months of initiation
  • Every 3-4 months thereafter
  • Conditional recommendation 1
• Lipids 1-2 months after starting treatment 1
• Dose adjustment: Discontinue if hemoglobin <8 g/dl or decreases >2 g/dl, or for severe neutropenia (<500/mm³) or lymphopenia (<500/mm³) 1

Emerging Biomarkers

While not yet part of standard guidelines, research suggests potential utility of:

• 14-3-3η protein: Found in approximately 30% of RF-positive and RF-negative polyarticular JIA patients; may represent a new biomarker particularly for RF-negative polyarticular JIA 5

• Cartilage Oligomeric Matrix Protein (COMP): Higher levels seen in early disease and in patients without joint erosions or joint space narrowing 4

Pitfalls and Caveats

• Normal inflammatory markers do not necessarily indicate absence of active disease 2
• Conversely, elevated inflammatory markers may persist even in clinically inactive disease 2
• A single laboratory test cannot confirm JIA activity; two or more abnormal parameters are more useful in assessing disease flares 3
• Laboratory monitoring recommendations are based on very low certainty evidence 1
• TB screening is conditionally recommended prior to starting biologic DMARD therapy and when there is concern for TB exposure 1