Impact of DXA acquisition mode on bone mineral density and longitudinal monitoring: Evidence from the Manitoba BMD registry.

Dual-energy X-ray absorptiometry (DXA) is the gold standard for assessing bone mineral density (BMD), but technical factors such as acquisition mode may affect measurement. On GE Healthcare DXA systems, Thin and Thick modes are often recommended for underweight and obese patients, respectively, while Standard mode is the default. Using the Manitoba Bone Density Program, a population-based registry, we analyzed paired same-day BMD measurements for the lumbar spine (n = 240), total hip (n = 432), and femoral neck (n = 431) obtained in Standard and nonstandard modes. Agreement was assessed by linear regression, Pearson correlation, Bland-Altman plots, and classification of BMD change using site-specific least significant change (LSC) thresholds. Paired Standard and nonstandard modes showed very strong correlations (r ≥ 0.97) with regression slopes approximating unity and intercepts approximating zero. Mean biases were negligible at the lumbar spine (-0.002 g/cm²), total hip (+0.001 g/cm²), and femoral neck (+0.001 g/cm²). Overall Standard versus nonstandard mode change agreement was near-perfect at the spine (Cohen's κ 0.89) and total hip (κ 0.81), and substantial at the femoral neck (κ 0.75). All observed scan mode differences fell well below established LSC thresholds. These findings demonstrate that Thin and Thick acquisition modes produce BMD results that are effectively interchangeable with Standard mode.