Reliability and validity of the telephone administration of the wheelchair outcome measure (WhOM) for middle-aged and older users of power mobility devices.

OBJECTIVE To examine the measurement properties of the tele-phone administration of the Wheelchair Outcome Measure (WhOM). SUBJECTS Power mobility device users aged 50-89 years. METHODS Two independent cohorts were recruited: (i) a prospective cohort (n = 40) to estimate test-retest reliability and to determine the applicability of the telephone format, and (ii) a cross-sectional cohort to examine construct validity with 3 groups: (a) people waiting for a first power mobility device (n = 44); (b) initial users (n = 35; 1-6 months); and (c) long-term users (n = 39; 12-18 months). RESULTS The tool demonstrated good test-retest reliability (intraclass correlation coefficient 0.77-1.00), took 10.9 min (standard deviation = 5.2) to administer and was practical to use over the telephone. Validity testing showed moderate correlations with the Quebec User Evaluation of Satisfaction with Technology (rS = 0.36-0.45) and the Psychosocial Impact of Assistive Devices Scale (rS = 0.31-0.43). WhOM scores could discriminate non-users from users (wait-list vs initial users; wait-list vs long-term users, p < 0.001) and power wheelchair from scooter users (total WhOM scores, p < 0.05). CONCLUSION The WhOM is a stable, valid and applicable measure for telephone administration with older power mobility device users. It is moderately linked to satisfaction with the device and to the psychosocial impact of the device, and therefore complements rather than replaces those measures.