Six Patient-Reported Outcome Measurement Information System Short Form Measures Have Negligible Age- or Diagnosis-Related Differential Item Functioning in Individuals With Disabilities

Cook KF, Bamer AM, Amtmann D, Molton IR, Jensen MP. Six Patient-Reported Outcome Measurement Information System short form measures have negligible age- or diagnosis-related differential item functioning in individuals with disabilities. Arch Phys Med Rehabil 2012;93:1289-91. Objective: To evaluate the measurement invariance of 6 self-report measures selected for an ongoing longitudinal study of individuals with spinal cord injury, muscular dystrophy, postpolio syndrome, and multiple sclerosis. Design: Participants completed and returned by mail surveys that included the targeted self-report measures. Ordinal logistic regressions methods were applied to evaluate items for differential item functioning (DIF) by diagnosis and age range. Setting: Community. Participants: Participants (N=2479) who had 1 of the 4 target diagnoses. Interventions: None. Main Outcome Measures: Six short-form measures from the Patient-Reported Outcome Measurement Information System (PROMIS) were administered to participants to measure fatigue, pain interference, satisfaction with social roles, sleep disturbance, sleep-related impairment, and depression. Results: One item of I measure (fatigue) exhibited DIF by diagnosis based on a published standard for meaningful DIF. However, scores corrected for this DIF were highly correlated with uncorrected scores (r>.999). No DIF by age range was found for any of the measures. Conclusions: Study findings support the use of the selected PROMIS short forms for comparing symptoms and quality of life indicators across different diagnoses and age ranges.