Estimation of T scores with Hologic using NatIve vs. Caucasian data in IndiAns (ETHNICA): a single center...

The Dual-energy X-ray absorptiometry (DXA) scan is considered the current gold standard for the estimation of bone mineral density (BMD). Normative BMD data for the generation of T scores is based on data pertaining to young Caucasian white women from the NHANES-III study. However, there have been reports of significant ethnic variations in the normal BMD values, which could under/over-diagnose osteoporosis. The Indian Council of Medical Research (ICMR) has given the normative BMD data for Indians. Our study compares machine-generated T-scores (T_std) based on Caucasian BMD reference data with calculated T-scores based on ICMR reference data (T_ICMR).

ETHNICA was a retrospective study involving 1144 individuals who underwent DXA study (Hologic^®) at our centre. 835 females and 309 males aged between 18 and 95 were included. A total of 3420 BMD values at bilateral hips and L1-L4 levels of spine were analysed. The age distribution differed from that of the NHANES-III and ICMR reference dataset, which primarily includes younger individuals (20-29 years) as it was done to standardize T score. Gender-specific ICMR BMD and standard deviation (SD) for each site were used to calculate T_ICMR. This was compared with Hologic-generated T_std, and the differences were analysed.

The prevalence of osteoporosis was significantly lower using ICMR data compared to NHANES-III data, with a greater reduction seen in males (16.8 to 7.1%) than in females (26.6 to 18%). Similarly, a larger increase in individuals classified with normal BMD was seen in males (59.5 to 76.1%) compared to females (41.2 to 59.6%).

We conclude that if we use NHANES-III BMD reference data, there is a significant overdiagnosis of osteoporosis and osteopenia in India. We recommend the adoption of representative regional reference standards for the diagnosis.