Analysis of stage-sequential change in rehabilitation research

The analysis of change is a critical topic for rehabilitation outcomes research, because the goal of rehabilitation is to improve patients' function. This article will sketch the issues and problems in statistical methods for analysis of change. Recovery after serious illness or injury often has been described in terms of transitions between a series of stages, but these theories of recovery have rarely been subjected to adequate statistical examination. This article presents two methods for the analysis of change, suitable for ordinal measures of function and for testing either simple cumulative or complex multipath stage-models of recovery. Progress in medical rehabilitation will be enhanced by explicitly specifying models of recovery, measuring recovery at multiple time points, and using the resulting data to test these models empirically.