TAMARA VOKES 1, DISHA KUMAR 1, MAUREEN COSTELLO 1 AND DIDIER HANS 2 UNIVERSITY OF CHICAGO MEDICINE, CHICAGO, ILLINOIS, USA 1 CENTER OF BONE DISEASES, LAUSANNE UNIVERSITY HOSPITAL, LAUSANNE SWITZERLAND 2 Racial Differences in TBS

Background Trabecular Bone Score (TBS) is Non-invasive method for assessing bone structure Predicts facture risk independent of BMD African Americans have lower fracture rates compared to Caucasians  Only partly explained by the higher BMD in African Americans

Objective Determine whether African Americans also have higher TBS (stronger bone) than Caucasians

Methods Subjects: 350 women (60% African American) referred for bone densitometry as part of routine clinical care Procedures: BMD, TBS, and presence of vertebral fractures on VFA using Prodigy

Results - demographics Vertebral fractures (grade 2 and 3) were present in 12% of women of both races African American women had higher age (70 vs 66, p=0.001), BMI (29 vs 27, p=0.001), and BMD T- scores at all skeletal sites (lowest of hip and spine T- score -1.7 vs -2.1, p=0.0007)

Results – TBS and other variables TBS was  Negatively correlated with age in Caucasians (p<0.001) but not in African Americans  Positively correlated with BMI in African Americans (p<0.001) but not in Caucasians  Positively correlated with spine BMD in both races (p<0.001) In a multivariate analysis, the association between TBS with age, BMI, and spine BMD was similar to that seen in univariate analysis

TBS in AA vs CA TBS was lower in African Americans (1.27 vs 1.30, p=0.015) and this difference became less significant when controlling for age (p=0.06) but more significant when controlling for BMI (p=0.002), spine BMD (p<0.001), or age AND BMI AND spine BMD (p<0.001)

TBS and Vfx Among Caucasian women, TBS was lower in those with compared to those without vertebral fractures (1.20 vs 1.31, p=0.002) Among African American women, TBS did not differ between those with and without vertebral fractures (1.26 for both) Among Caucasian subjects, T-scores at all skeletal sites were significantly lower in those with vertebral fractures while among African Americans the differences were smaller and not statistically significant

Conclusions There may be a racial difference in the relationship between TBS and other predictors of bone fragility  This should be considered when using TBS in subjects of different races  Further studies are needed to explore the mechanisms underlying these observations which in turn may explain the reasons for racial differences in fracture rates