IntroductionThe STARx Questionnaire was designed with patient and provider input, to measure self-management and transition skills in adolescents and young adults (AYA) with chronic health conditions. With proven reliability and an empirically-based factor structure, the self-report STARx Questionnaire requires further validation to demonstrate its clinical and research utility. In this study we examine the concurrent, predictive, and discriminant validity of the STARx Questionnaire.MethodsTo examine concurrent validity, the STARx Questionnaire was compared to two other published transition readiness tools. Predictive validity was examined using linear regressions between the STARx Total Score and literacy, medication adherence, quality of life, and health services use. Discriminant validity was examined by comparing the performance of three chronic illness conditions on the STARx Total Score and associated subscales.ResultsThe STARx Questionnaire and its subscales positively correlated with the scores for both transition readiness tools reflecting strong concurrent validity. The STARx Questionnaire also correlated positively with the literacy, self-efficacy, and adherence measures indicating strong predictive validity; however, it did not correlate with either quality of life or health care utilization. The performance of AYA across three different clinical conditions was not significant, indicating the clinical utility of this HCT tool for a variety of chronic health conditions.ConclusionThe strong validity of the STARx Questionnaire, in tandem with its strong reliability, indicated adequate psychometric properties for this generic self-report measure. These strong psychometric properties should contribute to the STARx being a viable measure of health care transition for both research and clinical purposes.