A computer adaptive testing simulation applied to the FIM instrument motor component

Objective: To determine whether computer adaptive testing (CAT) can be used to decrease the number of FIM(TM) instrument motor component items administered in assessing persons with spinal cord injury (SCI). Design: For a CAT simulation, a 3-step algorithm was use to select 6 FIM items for each individual; items were selected according to the subject's motor ability as estimated by 2 initial items. Separate estimates of motor ability for admission, discharge, and follow-up data (plus combined time points) derived from 6 items were compared statistically with estimates derived from 14 items (walking and wheelchair mobility were split). Setting: Records from the Spinal Cord Injury Model Systems (SCIMS). Participants: Patients served by the SCIMS, for whom complete motor FIM information was available for rehabilitation admission (N=5969), discharge (N=5964), or follow-up at a first or later anniversary (N=5176). Interventions: Not applicable. Main Outcome Measures: Similarity of mean, standard deviation, skewness, kurtosis, and Rasch reliability and separation of persons and items based on 6 and 13 items; intraclass correlation coefficient (ICC) for parallel estimates. Results: Calibrations for FIM items and FIM steps differed for the 3 time points, but showed sufficient agreement (ICC, >.90) that combined calibration was feasible. Means and other distribution characteristics differed minimally between the 6- and 13-item estimates. The person and item separations and reliabilities were somewhat lower and the mean measurement errors somewhat higher for the 6-item estimates, but only marginally so. ICCs between 6- and 13-item estimates were .95 or higher. Conclusion: CAT can be used to reduce data collection time; the level of precision of estimates is minimally less than that provided by traditional assessment approaches.