Assessing physical function in the elderly.

This article emphasizes the complexity underlying the assessment of physical function. The concept of physical function is multidimensional; individuals or groups can be assessed; the assessments can be either preintervention measures or outcome measures. Six issues of measurement are discussed: verbal report versus behavior; self-reported versus proxy-reported information; capacity versus performance; assumptions in Activities of Daily Living and Instrumental Activities of Daily Living measurement; differences between items and instruments; and the search for a summary index. Specific instruments are reviewed.