Comparison between Horizon A System and Lunar iDXA in Bone Assessment and Osteoporosis Diagnosis: The OsteoLaus Cohort

To compare the values of the bone mineral density (BMD) T-score between two Dual- energy X-ray Absorptiometry (DXA) devices of the latest generation: Horizon A System® (Hologic, Waltham, MA, USA) and Lunar iDXA® (GE Healthcare, Madison, Wi, USA), as measured in the total hip (TH), femoral neck (FN) and lumbar spine (LS). DXA is the standard bone imaging technique used for the BMD assessment and the eventual of the osteoporosis diagnosis as based on the BMD T-score. Post-menopausal women of the 5th visit of the OsteoLaus Cohort underwent DXA assessments with both devices in the same day, within one hour. Two technicians: one for Horizon A and one for Lunar iDXA performed all the scans. T-tests were used to compare the TH, FN and LS BMD T-scores between the two DXAs. Participants were classified as osteoporotic (lowest BMD T-score ≤ -2.5 SD), osteopenic (lowest BMD T-score ≤ -1.0 SD) or normal (lowest BMD T-score > -1 SD), separately for each DXA device. A contingency table was used to compare this classification between the two devices. 789 participants were analyzed (age 72.6±6.9 years, BMI 25.8±4.9 kg/cm2). As expected, Lunar iDXA measured higher mean values in g/cm2 of TH and LS BMD (statistically significant (p< 0.001), and of FN BMD (not significant), as compared to Horizon A. Regarding the BMD T- Scores, Lunar iDXA measured lower mean values for FN (-0.116±0.288), TH (-0.179±0.255) and LS (-0.191±0.426) compared to Horizon A. The prevalence of densitometric osteoporosis was 26,6% on Lunar iDXA and 22,7% on Horizon A, with an overall agreement of 82% (cf. contingency table). BMD values were higher as measured by the Lunar iDXA than by the Hologic A System. Interestingly, BMD T- Scores were lower as measured by the Lunar iDXA than by the Hologic A System. At the individual level, these differences between devices impact the diagnostic of densitometric osteoporosis. Further studies including the presence of fragility fractures are planned to analyze how these DXA devices discriminate fragility fractures as based on the BMD T-Scores.