QUALITY-CONTROL OF DXA INSTRUMENTS IN MULTICENTER TRIALS

Dual-energy X-ray absorptiometry (DXA) has become the measurement of c hoice for multicenter trials with bone density endpoints. When perform ing DXA measurements with several different systems, it is important t o implement a quality assurance program to guarantee that any observed density changes are real and not due to machine and/or operator varia bility. In this study, we present a series of procedures based on phan tom measurements designed to monitor DXA instrument stability. Techniq ues for longitudinal evaluation of machine performance and cross-calib ration of instruments are described. These procedures are then demonst rated using quality assurance data collected from a number of differen t DXA scanners. Together these methods provide a defined approach to i nstrument quality control. Though based primarily on the use of spinal phantoms, these procedures can be generalized for use in any multicen ter DXA study.