Measurement Properties of Functional Activity and Quality of Life Questionnaires in Children with Fibromyalgia

Abstract

Objectives: The study evaluated the measurement properties of functional activity and quality of life questionnaires in children with fibromyalgia(FM) using the population of children with FM involved in a randomized controlled pilot trial of an aerobic exercise program (Fibromyalgia Impact Trial). Methods: Children with FM (8-18 years old, n=30) participated in three sessions of testing (two preintervention and one postintervention ) 2-6 weeks apart for the Fibromyalgia Impact Trial. The participants completed the Childhood Health Assessment Questionnaire (C-HAQ), the Quality of My Life (QOML) scale, the Pediatric Quality of Life Inventory (PedsQL) fatigue and pain score, the Functional Status and Symptom Questionnaire (FSSQ), the Childhood Depression Inventory (CDI), and the Habitual Activity Estimation Scale (HAES) at testing times. We evaluated the validity, reliability, and responsiveness of these questionnaires. For construct validity, we estimated the Spearman correlation coefficient between the scales. The test-retest reliability was evaluated by calculating the intrarater intraclass correlation coefficient, the limits of agreement and the standard error of measurement with the 95% confidence intervals between test 1 and test 2. Responsiveness of each scale was assessed using the effect size and the standardized response mean. Results: The PedsQL fatigue score demonstrated high test-retest reliability and responsiveness. Negative strong significant correlation was seen between the scores of fatigue measured by PedsQL and depression measured by CDI. CDI showed the highest test-retest reliability and moderate responsiveness. C-HAQ total score with 8 domains demonstrated excellent agreement and poor responsiveness. Correlation between fatigue measured by PedsQL and overall rating of illness by C-HAQ was moderate to strong in magnitude and negative in direction. Conclusion: Functional activity and quality of life scales can be used effectively for patient reported outcomes among children with FM. However, investigators should be aware of the limitations of instruments used for evaluation of patient reported outcomes in this population. Further research is needed with larger sample size to support the results of the current study.