RESUMO
OBJECTIVES: To test the internal consistency and item difficulty of the modified Iowa Level of Assistance Scale (mILAS). DESIGN: Retrospective observational study. SETTING: Two orthopaedic wards of two general hospitals. PARTICIPANTS: Following elective primary unilateral total hip replacement surgery, all participants performed mILAS activities that were scored daily to assess their recovery of activities during hospitalisation. MAIN OUTCOME MEASURES: The internal consistency and the level of assistance needed by the patient (item difficulty) of the mILAS were calculated using data from Deventer Hospital, Deventer, the Netherlands (n=255). A cross-validation was performed using data from Nij Smellinghe Hospital, Drachten, the Netherlands (n=224). RESULTS: The internal consistency of the mILAS was acceptable on all three postoperative days (α=0.84 to 0.97). Cronbach's α and Rasch analysis revealed a misfit of stair climbing with the other items of the mILAS. The item difficulty of the mILAS items changed over the first two postoperative days. During the first three postoperative days, the sit to supine transfer was generally the most difficult item to achieve, and the sit to stand transfer was the least difficult item to achieve as rated by physiotherapists. The cross-validation analysis revealed similar results. CONCLUSIONS: The mILAS is a clinically sound measurement tool to assess the ability of patients to perform five functional tasks safely during hospitalisation. Stair climbing appears to be the easiest item to complete, and the sit to supine transfer is generally the most difficult after surgery.