Proposed criteria for appraising goal attainment scales used as outcome measures in rehabilitation research

Goal Attainment Scaling (GAS) is a method for writing personalized evaluation scales to quantify progress toward defined rehabilitation goals. In the published literature, GAS methodology is used with different levels of rigor, ranging from precisely written GAS scales that ensure minimal bias and explicitly describe 5 levels of goal attainment to subjective ratings of goal attainment by adjectives (eg, worse/better than expected), which are transformed into a T score, wrongly giving the reader the impression of a truly standardized, interval scale. A drawback of GAS methodology is that it is highly dependent on the ability of the GAS setting team/person to generate valid, reliable, and meaningful scales; therefore, reliability and validity of GAS scales are idiosyncratic to each study. The aims of this article were to (1) increase awareness of potential sources of bias in GAS processes; (2) propose GAS quality appraisal criteria, allowing judgment of the quality of GAS methodology in individual rehabilitation studies; and (3) propose directions to improve GAS implementation to increase its reliability and validity as a research measurement tool. Our proposed quality appraisal criteria are based on critical appraisal of GAS literature and published GAS validity studies that have demonstrated that precision, validity, and reliability can be obtained when using GAS as an outcome measure in clinical trials. We recommend that authors using GAS report accurately how GAS methodology was used based on these criteria