Interpreting Change Scores of Tests and Measures Used in Physical Therapy

TLDR

Over the past decade, methods and science describing changes in physical therapy outcomes have become more refined, with recent emphasis on changes beyond measurement error and those that truly impact patients and families. The article presents a case example and offers recommendations for physical therapists on interpreting clinically significant change in practice, case reports, and research. The authors use item maps within an item response theory model to enhance content‑level interpretation of change. The recommendations promote broader use of indexes that clarify clinically significant change for clinicians, researchers, consumers, and payers.

Abstract

Abstract Over the past decade, the methods and science used to describe changes in outcomes of physical therapy services have become more refined. Recently, emphasis has been placed not only on changes beyond expected measurement error, but also on the identification of changes that make a real difference in the lives of patients and families. This article will highlight a case example of how to determine and interpret “clinically significant change” from both of these perspectives. The authors also examine how to use item maps within an item response theory model to enhance the interpretation of change at a content level. Recommendations are provided for physical therapists who are interpreting changes in the context of clinical practice, case reports, and intervention research. These recommendations include a greater application of indexes that help interpret the meaning of clinically significant change to multiple clinical, research, consumer, and payer communities.