Global rating of change scales: a review of strengths and weaknesses and considerations for design.

Most clinicians ask their patients to rate whether their health condition has improved or deteriorated over time and then use this information to guide management decisions. Many studies also use patient-rated change as an outcome measure to determine the efficacy of a particular treatment. Global rating of change (GRC) scales provide a method of obtaining this information in a manner that is quick, flexible, and efficient. As with any outcome measure, however, meaningful interpretation of results can only be undertaken with due consideration of the clinimetric properties, strengths, and weaknesses of the instrument. The purpose of this article is to summarize this information to assist appropriate interpretation of the GRC results and to provide evidence-informed advice to guide design and administration of GRC scales. These considerations are relevant and applicable to the use of GRC scales both in the clinic and in research.