Effects of Body Positioning When Assessing Lymphedema of the Lower Limb Using Bioimpedance Spectroscopy.

Background: Bioimpedance spectroscopy (BIS) measurements are conventionally performed in supine position with a lead device attached to gel-backed electrodes, and more recently, with a stand-on device that uses fixed stainless-steel electrodes under the hands and feet. The aim of this study was to assess and compare BIS measurements made in supine, sitting, and standing positions using lead and stand-on impedance devices in participants with and without unilateral leg lymphedema. Materials and Methods: Participants with self-ascribed unilateral leg lymphedema ( n  = 24) and healthy controls ( n  = 71) were recruited using a cross-sectional study design. Triplicate BIS measurements were taken for each device in each position. Results: Impedance measurements with either device were reliable with coefficient of variation of 0.6% or lower. The magnitude of mean differences in absolute impedance values between devices were between 1% and 6% dependent on condition. L-Dex scores between the two devices were highly correlated ( r  = 0.82) and ∼70% of participants in the lymphedema group were classified as having lymphedema using the recommended cut-off with either device. There was no significant interleg difference of controls using the lead device; however, small, but significant differences ( p  = 0.0001) were found when using the stand-on device. Conclusion: The findings demonstrate that reliable impedance measurements of the legs can be made with either device in lying, sitting, or standing positions. However, data between the devices were not directly interchangeable. Although the risk of misidentification was small, reference ranges appropriate to the device and measurement position should be used when converting data to L-Dex scores.