Generalizability studies of the Global Assessment of Functioning–Split version

ObjectiveThe study aimed to use the Generalizability Theory to investigate the reliability and precision of the split version of the Global Assessment of Functioning (GAF).MaterialsSix case vignettes were assessed by 2 samples; one by 19 experienced and independent raters and another by 58 experienced raters from 8 different day-treatment units, evaluating both symptom and function scores of GAF.MethodsGeneralizability studies were conducted to disentangle relevant variance components accounting for error variance in GAF scores. Furthermore, decision studies were conducted to estimate the reliability of different measurement designs, as well as precision in terms of error tolerance ratio.ResultsBoth symptom and function scores of GAF were found to be highly generalizable, and a measurement design of 2 raters per subject was found to be most efficient with respect to reliability, precision, and use of resources.ConclusionBoth symptom and function scores of GAF seem highly consistent across experienced raters.