Comparing three preprocessing strategies for longitudinal data: An example in functional outcomes research

Longitudinal monitoring of individual patient data is becoming routine in physician office practice. This study compares three different methods for evaluating clinical outcomes for individual patients: raw change score analysis versus normative and ipsative statistical analyses. Two discrete samples of intermittent claudication patients making vascular surgery office visits - drawn from interventional management versus stable, routinely followed control groups - were tested four times using both generic and disease-specific functional status measures. Results indicated that the ipsative method was most consistent with several different types of a priori hypotheses that are often evaluated in analysis of repeated measures data.