RESUMEN
Introduction: Professionalism is a key quality that medical students should possess, but it is difficult to define and assess. Current assess-ment tools have room for improvement. This study aimed to design and validate a self-assessment tool to assess professionalism among medical students. Method: A questionnaire was created based on 10 tenets of professionalism from the Charter on Medical Professionalism jointly published by the American Board of Internal Medicine Foundation, American College of Physicians Foundation and European Federation of Internal Medicine, along with input from Singapore guides. The self-administered questionnaire was administered to Year 2 to 5 students from Yong Loo Lin School of Medicine, National University of Singapore in a voluntary, anonymised manner in the academic year of 2019/2020. Construct validity and internal reliability were evaluated using Principal Component Analysis (PCA) and Cronbach's alpha, respectively. Results: There was a total of 541 respondents. After removing incomplete responses, 504 responses were included. Following PCA, a 17-item questionnaire titled "Medical Professionalism: A Self-assessment Tool" (MPAST) with a 5-component solution was obtained. The 5 components were commit-ment to: (1) patient's best interest, (2) honesty and integrity, (3) professional competency, (4) patient safety and care, and (5) educational responsibilities. Their Cronbach's alpha value ranged from 0.540 to 0.714, with an overall Cronbach's alpha value of 0.777. Conclusion: MPAST is valid, reliable, practical, and is the first validated self-assessment tool to assess professional attributes and behaviours among medical students, to our knowledge.