Score comparability of short forms and computerized adaptive testing: Simulation study with the activity measure for post-acute care.

OBJECTIVE: To compare simulated short-form and computerized adaptive testing (CAT) scores to scores obtained from complete item sets for each of the 3 domains of the Activity Measure for Post-Acute Care (AM-PAC).
DESIGN: Prospective study.
SETTING: Six postacute health care networks in the greater Boston metropolitan area, including inpatient acute rehabilitation, transitional care units, home care, and outpatient services. PARTICIPANTS: A convenience sample of 485 adult volunteers who were receiving skilled rehabilitation services.
INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Inpatient and community-based short forms and CAT applications were developed for each of 3 activity domains (physical & mobility, personal care & instrumental, applied cognition) using item pools constructed from new items and items from existing postacute care instruments.
RESULTS: Simulated CAT scores correlated highly with score estimates from the total item pool in each domain (4- and 6-item CAT r range,.90-.95; 10-item CAT r range,.96-.98). Scores on the 10-item short forms constructed for inpatient and community settings also provided good estimates of the AM-PAC item pool scores for the physical & movement and personal care & instrumental domains, but were less consistent in the applied cognition domain. Confidence intervals around individual scores were greater in the short forms than for the CATs.
CONCLUSIONS: Accurate scoring estimates for AM-PAC domains can be obtained with either the setting-specific short forms or the CATs. The strong relationship between CAT and item pool scores can be attributed to the CAT's ability to select specific items to match individual responses. The CAT may have additional advantages over short forms in practicality, efficiency, and the potential for providing more precise scoring estimates for individuals.