Reporting of long-term extension studies: lack of consistency calls for consensus

Double-blind, randomised controlled studies represent the gold-standard approach to determine the safety and efficacy of therapeutic interventions. In chronic conditions such as rheumatoid arthritis (RA), long-term data are vital to confirm maintenance of effect and identify potential safety signals. The recent introduction of numerous biological therapies for RA has been followed by various long-term extension (LTE) studies. Although useful, the design and method of analysis in such studies vary significantly, partly due to their complexity. This viewpoint highlights general considerations needed when undertaking a LTE study and illustrates the lack of consistency in studies of RA to date. It addresses issues of selection bias, patient discontinuation and missing data. Although used for safety reporting, the lack of adequate powering makes LTE studies of limited benefit. Ethical considerations and challenges are highlighted, including potential conflicts of interest. Finally, the authors suggest the need for consensus to ensure more reliable interpretation and application of data for clinical practice. Following the development of guidelines on reporting of clinical trials in RA and more recently, registry data, a similar approach for LTE studies would be a useful endeavour.