Evaluating the FONE FIM: Part I. Construct validity.

Rasch analysis was used in this paper to evaluate the Motor component of the FONE FIM, the telephone version of the Functional Independence Measure (FIM). For this purpose, 132 patients discharged from an inpatient geriatric assessment and rehabilitation program were assessed by trained research assistants using the FONE FIM. The results at 5 weeks post-discharge were compared to the observation FIMs (OBS FIMs) done at home 6 weeks post-discharge. These patients had an average age of 79 years and presented with multiple, complex medical problems and significant functional decline. The FONE FIM and the OBS FIM were shown to share a strikingly similar item hierarchy, based on Rasch item difficulty measures. Only bladder management and climbing stairs were misfitting items as indicated by item fit statistics. The same 13-item set and 4-point scales were shown to be psychometrically optimal for both the FONE FIM and the OBS FIM based on the person separation index. Further research is required to address the issue of the optimal item set and scale levels from psychometric and clinical perspectives.