Second, only two of the three major DXA manufacturers’ systems were included in the study. Thus, we could not validate any of the sBMD relationships involving Norland systems. Third, our findings are only strictly applicable when the spine-positioning block is used for the Hologic systems and not used on the GE-Lunar systems. Currently, the GE-Lunar Prodigy can be used GSK2118436 order with the positioning block or without it using the Onescan™ option. Lastly, our study was not able to determine which of the many differences between the pencil and fan-beam systems was responsible

for the differences seen at the spine. The time and reason for the change in inter-manufacturer accuracy is important to determine since studies often involve different models and software versions. The pencil-beam sBMD equations made comparing BMD measurements for studies using different DXA systems possible. Pencil-beam technology has all but been totally replaced with fan-beam systems due to faster scan times, improved image quality, and greater measurement precision. It is important to note that neither sBMD nor the cross-calibration Nirogacestat ic50 equations derived in this study solve the problem of comparing the DXA results of a patient done at one clinic on a Hologic scanner to those done at a second clinic on a GE-Lunar scanner. The large SEE of the standardization

(or conversion) equations, which in this study was in the range of 4–7%, prevents a precise comparison of the BMD of an individual between scanners from different manufacturers. As previously pointed out by Formica [19] and Ozdemir and Ucar [11], these equations are most useful for pooling data from multi-center trials to remove systematic differences and not for comparing results of individual patients. In conclusion, this study found that marked systematic differences in BMD values between current generation fan-beam DXA systems are reduced when using the sBMD equations, but residual differences remain especially for the spine ROIs.

Etofibrate New relationships were derived from cross-calibration data averaged between three clinical sites that removed the systematic differences at all ROIs. This study emphasizes the need to keep standardization equations up to date with advances in technology and clinical practice to ensure accuracy when pooling results between scanners. Acknowledgments The authors would like to thank GE-Lunar and Hologic who provided partial funding for this study and Jenny Sherman for her editing of the manuscript. We also acknowledge the contributions of Paul Miller and Mike Lewiecki of the Colorado Center for Bone Research, Lakewood, Colorado, and the New Mexico Clinical Research & Osteoporosis Center, Albuquerque, New Mexico, as clinical data collection sites.