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Obesity increases precision errors in dual-energy X-ray absorptiometry measurements
Karen M Knapp1, Joanne R Welsman, Susan J Hopkins
1Department of Medical Imaging, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK. K.M.Knapp@exeter.ac.uk
Summary
Body mass index (BMI) impacts dual-energy X-ray absorptiometry (DXA) precision. Higher BMI in obese individuals increases measurement errors for lumbar spine and hip bone mineral density, requiring cautious interpretation of serial DXA scans.
Area of Science:
- Medical Imaging
- Bone Densitometry
- Osteoporosis Research
Background:
- Dual-energy X-ray absorptiometry (DXA) is crucial for monitoring bone mineral density (BMD) and osteoporosis.
- Precision errors in DXA measurements can affect the accuracy of longitudinal BMD assessments.
- The influence of body mass index (BMI) on DXA precision requires further investigation.
Purpose of the Study:
- To evaluate the impact of different body mass index (BMI) categories on the precision errors of bone mineral density (BMD) measurements.
- To determine if BMI affects DXA measurement precision at the lumbar spine (LS), femoral neck (NOF), total hip (TH), and total body (TB).
Main Methods:
- One hundred two women with a wide range of BMIs (18.5–45.9 kg/m²) underwent duplicate DXA scans with repositioning.
- Participants were stratified into normal (<25 kg/m²), overweight (25–30 kg/m²), and obese (>30 kg/m²) BMI groups.
- Precision was assessed using the percentage coefficient of variation (%CV) for LS, NOF, TH, and TB BMD.
Main Results:
- Precision errors (%CV) increased with higher BMI categories across most sites.
- Obese group showed significantly higher precision errors for LS BMD (1.68%), NOF BMD (2.00%), and TB BMD (0.91%) compared to the normal group.
- Statistically significant differences in precision error were observed between normal and obese groups for LS (p=0.0006), NOF (p=0.005), and TB BMD (p=0.025).
Conclusions:
- Higher body mass index (BMI) is associated with increased precision errors in dual-energy X-ray absorptiometry (DXA) measurements.
- Serial DXA measurements in obese individuals should be interpreted with caution due to potentially larger least significant change.
- These findings highlight the need to consider BMI when assessing DXA measurement variability and clinical significance.
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