QUALITY ASSURANCE FOR BONE DENSITOMETRY RESEARCH STUDIES - CONCEPT AND IMPACT

A concept for quality assurance (QA) in bone densitometry has been dev eloped for clinical multicenter studies. Major elements provided by a coordinating center comprise (1) consulting services and certification of participating centers in the start-up phase of the study, (2) revi ew of scan data acquired on QA standards for cross-calibration and lon gitudinal assessment of scanner stability, (3) review of selected pati ent data as well as of problem cases during the study, and (4) compreh ensive review and correction of patient results based on QA data after conclusion of the study. Limitations of phantom-based QA data should be acknowledged. Typical problems encountered during research studies and guidelines for solutions are presented. Successful implementation of QA measures may yield substantial enhancement of statistical power. Depending on the study design and the variability of response within patient groups, improvement in precision due to QA measures may reduce the smallest detectable difference between subject groups or, alterna tively, sample size by a few to more than 50%, and thus may contribute to a substantial reduction in study cost. Formulae for calculation of the magnitude of these effects are presented. To maximize the net ben efit, QA efforts have to be limited to levels that assure reliability of the data at acceptable QA cost. While QA programs at individual cli nical sites or for local practitioners may not need to be as extensive as for multicenter clinical trials, awareness of the potential proble ms and implementation of basic QA measures will help in obtaining high -quality bone densitometry results.