The Fat Mass Does Not Influence Precision Error of Trabecular Bone Score: An in Vivo Study

Purpose: Trabecular bone score (TBS) is a measurement of the trabecular microarchitecture obtained from lumbar spine dual-energy X-ray absorptiometry. A previous phantom study showed that increased soft tissue thickness does not affect TBS reproducibility. We investigated the in vivo effect of increased body mass index (BMI) and waist circumference on TBS precision error.

Methods and Materials: A population of postmenopausal white women was distributed in three different BMI groups (normal, overweight, and class I obesity), plus two further groups based on waist circumference (≤ 88 cm and > 88 cm, respectively). In vivo precision error was calculated on 30 consecutive subjects who were scanned twice, with patient repositioning, using the Hologic QDR-Discovery W densitometer. Coefficient of variation, percentage least significant change, and reproducibility were calculated according to the International Society for Clinical Densitometry guidelines.

Results: A total of 95 women aged 66 ± 10 (mean ± standard deviation) were included. No significant differences were found both in BMD and TBS precision errors, respectively, when comparing BMI groups and waist circumference groups. BMD reproducibility ranged from 95.9% (BMI > 30 kg/m²) to 97.5% (BMI < 25 kg/m²). TBS reproducibility ranged between 95.8% (BMI: 25–29.9 kg/m²; waist circumference > 88 cm) and 96.6% (BMI < 25 kg/m²). With the exception of the obese group, a significant difference was found between BMD and TBS reproducibility: TBS was slightly lower than BMD. A significant decrease of TBS values was found between normal and obese subjects, as well as between waist circumference groups; BMD variations between groups were not statistically significant.

Conclusion: TBS precision error is not affected by BMI and waist circumference differences. TBS reproducibility was shown to be slightly lower than that of BMD, but this difference was mitigated in obese patients. We confirmed the detrimental effect of fat mass on TBS.

No conflict of interest has been declared by the author(s).