ACR score is a scale to measure change in rheumatoid arthritis symptoms. It is named after the American College of Rheumatology. Different degrees of improvement are referred to as ACR20, ACR50, ACR70. The ACR score is more often used in clinical trials than in doctor patient-relationships, as it allows a 'common standard' between researchers. The Rheumatoid Arthritis Severity Scale (RASS) is based on sections of the ACR scoring system.