Validation of the Childhood Health Assessment Questionnaire in active juvenile systemic lupus erythematosus

Objective. To validate the Childhood Health Assessment Questionnaire (C-HAQ) as a measure of disability in patients with active juvenile systemic lupus erythematosus (SLE). Methods. Of 557 patients with juvenile SLE included in the Paediatric Rheumatology International Trials Organisation (PRINTO) database, 504 (90.5%) were included in the present study and underwent C-HAQ assessment at the time of a major therapeutic intervention and then after 6 months. Validation procedures, according to the Outcome Measures in Rheumatology Clinical Trials filter for outcome measures in rheumatology, included assessment of responsiveness, feasibility, internal consistency, construct validity, collinearity, and discriminative ability. Response to therapy was evaluated with the PRINTO/American College of Rheumatology (ACR) juvenile SLE definition of improvement. Results. At baseline, patients showed a high level of disease activity (mean physician global 5.8) and moderate disability (mean C-HAQ 0.83); both disease activity and disability improved after 6 months of treatment. The change in C-HAQ score correlated moderately with the Systemic Lupus Activity Measure (r s = 0.42), parent's global assessment of pain and well-being (r s = 0.55 and 0.53, respectively), and the physical summary score of the Child Health Questionnaire (r s = -0.61), and poorly with other clinical and laboratory parameters. The absolute change in C-HAQ demonstrated a significant ability to discriminate between patients who improved and those who did not improve based on the PRINTO/ACR definition of improvement. Responsiveness of the C-HAQ was moderate (standardized response mean 0.74). Internal consistency was excellent (Cronbach's α = 0.96). Conclusion. The C-HAQ showed moderate responsiveness to clinical change, construct validity, good feasibility, internal consistency, and discriminative ability. These findings demonstrate that the C-HAQ represents a good measure to capture disability in patients with active juvenile SLE.