Measuring Mobility in Low Functioning Hospital Patients: An AM-PAC Replenishment Project

Objective To expand an existing validated measure of basic mobility (Activity Measure for Post-Acute Care [AM-PAC]) for patients at the lowest levels of function. Design Item replenishment for existing item response theory (IRT) derived measure via (1) idea generation and creation of potential new items, (2) item calibration and field testing, and (3) longitudinal pilot test. Setting Two tertiary acute care hospitals. Participants Consecutive inpatients (N=502) ≥18 years old, with an AM-PAC Inpatient Mobility Short Form (IMSF) raw score ≤15. For the longitudinal pilot test, 8 inpatients were evaluated. Results Fifteen new AM-PAC items were developed, 2 of which improved mobility measurement at the lower levels of functioning. Specifically, with the 2 new items, the floor effect of the AM-PAC IMSF was reduced by 19%, statistical power and measurement breadth were greater, and there was greater measurement sensitivity in longitudinal pilot testing. Conclusion Adding 2 new items to the AM-PAC IMSF lowered the floor and increased statistical power, measurement breadth, and sensitivity.