Comparative study of bone mineral density using quantitative computed tomography to establish a local population reference standard and comparison with existing osteoporosis Standards: Insights from south India

Background: Early identification of reduced bone mineral density (BMD) and providing appropriate measures depending on BMD values, lead to early prevention and treatment of osteoporosis-related complications effectively. Quantification of osteoporosis can also be done by quantitative computed tomography (qCT). The present study was conducted to derive a reference standard BMD using phantomless qCT software for our local population of South India. Methods: A hospital-based cross-sectional study was conducted among patients >20 years of age who were undergoing a CT study which included T12, L1 & L2 vertebrae and were free of obvious bone pathology. The axial CT series was used to calculate the BMD. Using the average BMD, we obtained from the patients in the age group of 20–39 years, an average and a standard deviation were calculated. Later we recalculated the T scores for patients across all age groups using cross-tabulations to identify how many people were under the osteoporosis group in each of the standards [US standards ie; the University of California, San Francisco (UCSF) standards, World Health Organization (WHO) standards and locally derived standards). Results: The mean BMD for the age group of 20–39 years were obtained for both males and females as 149.4 mg/cc² and 152.5 mg/cc² respectively. Based on the bone attenuation in CT we found that attenuation >120 Hounsfield units (HU) did not have any osteoporosis and attenuation >200 HU did not have any osteopenia according to our reference standards. Similarly, when we considered the values of UCSF standards we found that attenuation >180 HU did not have any osteoporosis and attenuation >240 HU did not have any osteopenia whereas according to WHO standards attenuation >130 HU did not have any osteoporosis and attenuation >210 HU did not have any osteopenia. Conclusion: Given the enormous patient volume of body CT scanning currently performed in older adults for a wide variety of clinical indications, this represents a unique opportunity to expand osteoporosis screening.