Reference Ranges for Bone Mineral Density and Prevalence of Osteoporosis in Vietnamese Men and Women

Background: The aim of this study was to examine the effect of different reference ranges in bone mineral density on the diagnosis of osteoporosis. Methods: This cross-sectional study involved 357 men and 870 women aged between 18 and 89 years, who were randomly sampled from various districts within Ho Chi Minh City, Vietnam. BMD at the femoral neck, lumbar spine and whole body was measured by DXA (Hologic QDR4500). Polynomial regression models and bootstraps method were used to determine peak BMD and standard deviation (SD). Based on the two parameters, we computed T-scores (denoted by T-VN) for each individual in the study. A similar diagnosis was also done based on T-scores provided by the densitometer (T-DXA), which is based on the US White population (NHANES III). We then compared the concordance between T-VN and T-DXA in the classification of osteoporosis. Osteoporosis was defined according to the World Health Organization criteria. Results: In post-menopausal women, the prevalence of osteoporosis based on femoral neck T-VN was 29%, but when the diagnosis was based on T-DXA, the prevalence was 44%. In men aged 50+ years, the T-VN-based prevalence of osteoporosis was 10%, which was lower than T-DXA-based prevalence (30%). Among 177 women who were diagnosed with osteoporosis by T-DXA, 35% were actually osteopenia by T-VN. The kappa-statistic was 0.54 for women and 0.41 for men. Conclusion: These data suggest that the T-scores provided by the Hologic QDR4500 over-diagnosed osteoporosis in Vietnamese men and women. This over-diagnosis could lead to over-treatment and influence the decision of recruitment of participants in clinical trials.