Assessing sleep and pain among adults with myalgic encephalomyelitis/chronic fatigue syndrome: psychometric evaluation of the PROMIS® sleep and pain short forms

PURPOSE: To evaluate the psychometric properties of the patient-reported outcome measurement information system® (PROMIS) short forms for assessing sleep disturbance, sleep-related impairment, pain interference, and pain behavior, among adults with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). METHODS: Data came from the Multi-Site ME/CFS study conducted between 2012 and 2020 at seven ME/CFS specialty clinics across the USA. Baseline and follow-up data from ME/CFS and healthy control (HC) groups were used to examine ceiling/floor effects, internal consistency reliability, differential item functioning (DIF), known-groups validity, and responsiveness. RESULTS: A total of 945 participants completed the baseline assessment (602 ME/CFS and 338 HC) and 441 ME/CFS also completed the follow-up. The baseline mean T-scores of PROMIS sleep and pain measures ranged from 57.68 to 62.40, about one standard deviation above the national norm (T-score = 50). All four measures showed high internal consistency (ω = 0.92 to 0.97) and no substantial floor/ceiling effects. No DIF was detected by age or sex. Known-groups comparisons among ME/CFS groups with low, medium, and high functional impairment showed significant small-sized differences in scores (η(2) = 0.01 to 0.05) for the two sleep measures and small-to-medium-sized differences (η(2) = 0.01 to 0.15) for the two pain measures. ME/CFS participants had significantly worse scores than HC (η(2) = 0.35 to 0.45) for all four measures. Given the non-interventional nature of the study, responsiveness was evaluated as sensitivity to change over time and the pain interference measure showed an acceptable sensitivity. CONCLUSION: The PROMIS sleep and pain measures demonstrated satisfactory psychometric properties supporting their use in ME/CFS research and clinical practice.