The PedsQL™ as a patient-reported outcome in children and adolescents with fibromyalgia: an analysis of OMERACT domains

BACKGROUND Fibromyalgia is a chronic health condition characterized by widespread musculoskeletal pain, multiple tender points on physical examination, generalized muscular aching, stiffness, fatigue, nonrestorative sleep pattern, cognitive dysfunction, and mood disturbance. Recently, the Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT) Fibromyalgia Syndrome Workshop ranked and prioritized the domains that should be consistently measured in fibromyalgia clinical trials, specifically, pain, generic health-related quality of life, fatigue, sleep quality, and physical function. The focus of these deliberations was exclusively on adult patients, and to our knowledge, these domains have not been previously tested within a multidimensional framework in children and adolescents with fibromyalgia. METHODS An analysis to determine the feasibility, reliability, and validity of the PedsQL 4.0 (Pediatric Quality of Life Inventory) Generic Core Scales, PedsQL Multidimensional Fatigue Scale, and PedsQL Rheumatology Module Pain and Hurt Scale as patient-reported outcome (PRO) measures for pediatric patients with fibromyalgia. The PedsQL Scales were completed by 59 families in a pediatric rheumatology clinic in a large children's hospital. RESULTS The PedsQL evidenced minimal missing responses (0.53% patient self-report, 0.70% parent proxy-report), achieved excellent reliability for the Generic Core Scales Total Scale Score (alpha = 0.88 patient self-report, 0.87 parent proxy-report), the Multidimensional Fatigue Scale Total Scale Score (alpha = 0.94 patient self-report, 0.94 parent proxy-report), and acceptable reliability for the 4-item Rheumatology Module Pain and Hurt Scale (alpha = 0.68 patient self-report, 0.75 parent proxy-report). The PedsQL Generic Core Scales and Multidimensional Fatigue Scale significantly distinguished between pediatric patients with fibromyalgia and healthy children. Pediatric patients with fibromyalgia self-reported severely impaired physical and psychosocial functioning, significantly lower on most dimensions when compared to pediatric cancer patients receiving cancer treatment, and significantly lower on all dimensions than pediatric patients with other rheumatologic diseases. Patients with fibromyalgia self-reported significantly greater pain and fatigue than pediatric patients with other rheumatologic conditions, and generally more fatigue than pediatric patients receiving treatment for cancer. CONCLUSION The results demonstrate the excellent measurement properties of the PedsQL Scales in fibromyalgia. These PedsQL Scales measure constructs consistent with the recommended OMERACT Fibromyalgia Syndrome Workshop domains. The findings highlight the severely impaired HRQOL of pediatric patients with fibromyalgia. Regular monitoring of pediatric patients with fibromyalgia will help identify children and adolescents at risk for severely impaired HRQOL. These PedsQL Scales are appropriate outcome measures for clinical trials and health services research for pediatric patients with fibromyalgia.