Measuring health-related quality of life in MSA: the MSA-QoL

The objective of this study was to develop a new patient-reported outcome measure for patients with multiple system atrophy (MSA) and to test its psychometric properties. There were three stages. First, a pool of potential scale items was generated from in-depth patient interviews. Second, these items were administered, in the form of a questionnaire, to a sample of people with MSA and traditional psychometric methods used to develop a rating scale satisfying standard criteria for reliability and validity. Third, the psychometric properties of the rating scale were examined in a second sample. In stage one, a pool of 105 items was generated from 20 patient interviews. In stage two, a scale with three subscales (motor, 14 items; nonmotor, 12 items; emotional/social functioning, 14 items), satisfying standard criteria for reliability and validity, was developed from the response data of 317 patients with MSA (response rate 71%). In stage three, the scale was examined in 286 people with MSA. Missing data were low, scores in both subscales were evenly distributed, and floor and ceiling effects were small. Reliability was high (Cronbach's alpha 0.83-0.93; test-retest ICC 0.88-0.92). Validity was supported by the interscale correlations (r = 0.47-0.59), known group differences, and the magnitude and pattern of correlations with four other rating scales, disease severity, and disease duration. In conclusion, the patient-rated MSA health-related Quality of life scale (MSA-QoL) may be a suitable patient-reported scale for use in clinical trials and studies in MSA.