The Effects of Fluid Hydration Status on Ultrasound Muscle Measurement in Hemodialysis Patients

Validity of an ultrasound device to measure bone mineral density

This study aims to examine the validity and reliability of the UltraScan650™, a portable ultrasound device, used to measure BMD at the 1/3rd radius position. Fifty-two female first responders and healthcare providers were assessed using DXA (forearm, femur, lumbar, and total body) and the UltraScan650™. Fat and lean mass were also assessed using the DXA. Pearson correlations, Bland-Altman plots, t-tests, and linear regressions were used to assess validity. Intra-class correlation (ICC) coefficients were used to assess reliability. Inter-rater reliability and repeatability were good (ICC = 0.896 [0.818; 0.942], p < 0.001) and excellent (ICC = 0.917 [0.785; 0.989], p < 0.001), respectively. BMD as measured by the UltraScan650™ was weakly correlated to the DXA (r = 0.382 [0.121; 0.593], p = 0.0052). Bland-Altman plots revealed that the UltraScan650™ underestimated BMD (-0.0569 g/cm2), this was confirmed with a significant paired t-test (p < 0.001). A linear regression was performed (0.4744 × UltraScan650™ + 0.4170) to provide more information as to the issue of agreement. Bland-Altman plots revealed a negligible bias, supported by a paired t-test (p = 0.9978). Pearson's correlation revealed a significant relationship (r = -0.771 [-0.862; -0.631], p < 0.0001) between adjusted UltraScan650™-DXA and the average of the two scans (i.e., adjusted UltraScan650™ and DXA), suggesting a proportional constant error and proportional constant variability in measurements of BMD from the UltraScan650™. The UltraScan650™ is not a valid alternative to DXA for diagnostic purposes; however, the UltraScan650™ could be used as a screening tool in the clinical and research setting given the linear transformation is employed.