Variation in Measurement Results Using Bioimpedance Spectroscopy to Determine Extracellular Fluid of Upper Extremity

The L-Dex U400 is a recently developed measurement device to aid in the clinical assessment of unilateral lymphedema. Until now, little is known about variation in measurement results of the L-Dex U400. The aim of this study was to determine variation in measurement results in determining extracellular fluid of the arm with the L-Dex U400 under different measurement conditions on 2 days and to determine the reliability of these measurements in healthy subjects. Thirty participants were included. Participants were measured on 2 days, 2 weeks apart. Each day they were measured six times, 1st basic measurement, 2nd after a 10-minute rest period, 3rd second observer, 4th after drinking 200 mL of coffee and rest for 30 minutes on the examination couch, 5th after 30 minutes of cycling on an exercise bike at 50 W and 50-60 rounds per minute, and 6th after a 10-minute rest period. The variance due to participants was 68% of the total variance and 32% was error variance. Lin's concordance coefficient (CCC), a reliability measure, ranged from 0.935 (first day, 1st and 2nd measurement of observer 1) to 0.517 (first and second day after a 10-minute rest period after cycling). In two CCCs, the lower limits of the 95% confidence interval were higher than 0.750. Repeatability coefficient was smallest for the basic observations on day 2 (4.6) and largest after cycling (8.0). Clinical decision-making based on L-Dex U400 measurements should be regarded with caution because of moderate reliability.