The accurate interpretation of repeat DXA scan measurements and the understanding of what constitutes a true and meaningful change require knowledge of measurement error (precision) and least significant change. The interpretation of lumbar spine bone mineral density in particular can be confounded by artefacts and as such, the International Society for Clinical Densitometry (ISCD) recommends exclusion of individual vertebrae if they are affected by local structural change or an artefact. The aim of this study was to determine the precision of bone mineral density measures of individual and various configurations of vertebrae from PA lumbar spine scans. The study group comprised of 30 women (age 36.3 ± 6.5 years; height: 165.2 ± 5.7 cm; weight: 67.7 ± 12.6 kg) who each received 2 consecutive anterior-posterior lumbar spine scans (Lunar iDXA, GE Healthcare, Madison, WI), with repositioning. Precision errors varied by individual vertebrae and by different configurations of vertebrae but all were within the ISCD acceptable range of precision. For vertebrae configurations containing at least 2 vertebrae, precision error ranged from 0.005 to 0.008 RMS-SD (0.44%-0.70% CV). Of the individual vertebrae, the lowest precision error was observed at L4, and from the different configurations, for L2L3L4 and L1L2L3L4. In conclusion, this study group demonstrated excellent precision for BMD measurements of individual and various configurations of L1-L4 vertebrae using the GE Lunar iDXA densitometer.
Keywords: Bone; Bone mineral density; DXA; Measurement; Spine.
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