Reliability of 4 outcome measures in pediatric spinal muscular atrophy

Background: Spinal muscular atrophy is a common neurologic disorder of infants and children with a high mortality rate. Clinical trials have not been attempted in this population until recently. Objective: To demonstrate that 4 outcome measures are reliable for use in clinical trials in patients with spinal muscular atrophy. Design, Setting, Patients: Thirty-eight children with spinal muscular atrophy who fulfilled inclusion and exclusion criteria were enrolled at 5 pediatric centers for a reliability study. Paired samples statistics were performed comparing results of the qualifying variance visit with a fourth visit. Main Outcome Measures: Quantitative muscle testing and the Gross Motor Function Measure. Results: Thirty-four patients and 7 evaluators completed the study. Thirteen patients were aged 2 through 4 years and 21 were 5 through 17 years. The Gross Motor Function Measure was completed by 34 subjects. Six variables for pulmonary function tests were measured in 20 subjects. Quantitative muscle testing was performed on 21 subjects in 8 muscle groups. Thirty-three subjects completed the PedsQL Neuromuscular Module for Parents. The intraclass correlation coefficient and Bradley-Blackwood procedures indicated a very high level of agreement between measures. Conclusion: The Gross Motor Function Measure, pulmonary function tests, quantitative muscle testing, and quality of life are reliable outcome measures for clinical trials in pediatric spinal muscular atrophy.