Dual energy X-ray absorptiometry measurements in small subjects: Conditions affecting clinical measurements

Objective: To document the clinical and experimental situations that may affect DXA measurements in small subjects. Methods: 49 piglets (886g to 1100g) had measurements with either of two pencil beam densitometers (QDR 1000W and QDR 2000 Plus, Hologic Inc, Waltham, MA) using commercial infant (TWB) and adult whole body (AWB) software v5.71p and v5.71 respectively. AWB scans were analyzed with three additional software versions. 35 infants (2115 to 11564g) had IWB measurements. Results: DXA measurements of total weight, bone mineral content, bone area, bone mineral density, fat and lean mass from IWB scans (all piglets) and from AWB scans (piglets > 12 kg) were highly reproducible (p < 0.001). A statistically significant change occurred in at least one of the DXA measurements from the use of different platforms, variations in the amount and placement of covering (e.g., blanket), placement of the external calibration standard, presence of radiographic contrast material, presence of movement artifact, delivery of an intravenous fluid bolus prior to scanning or improper delineation of external calibration standard during analysis. Additionally, results varied amongst different versions of software as well as between IWB and AWB softwares. Conclusion: In small subjects, consistency in the DXA techniques is paramount for valid and meaningful comparison of DXA data in bone mass and body composition.