Background
Validated health-related quality of life (HRQOL) instruments may require updating as they begin to be used in randomised controlled trials (RCTs) containing patient populations and novel drugs that did not form part of the original validation study. Multiple myeloma (MM) is one example where new classes of drugs are rapidly emerging. There are a number of commonly used HRQOL instruments used, some generic and some MM specific but it is unclear how valid existing instruments will be in RCTs of novel agents. We aim to make recommendations for ongoing validation of HRQOL instruments in RCTs applicable to many disease areas using empirical evidence from the case of MM.