The dichotomization of change scores to classify patients as either clinically improved or non-clinically improved is a simple method to clarify results derived from patient-reported outcome measures. It appears that both direct methods, using Global Perceived Effect (GPE) scales, and indirect methods, using distribution- and anchor-based methods, have a number of strengths and limitiations. Moreover, there is convergence between the different methods of achieving the proportion of patients improved and, thus, it is difficult to recommend a single method for its determination.
It is suggested that patients be categorized into clinically improved and clinically non-improved groups using a selection of procedures composed of a direct method and indirect methods including both distribution- and anchor-based approaches.
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