Normative Interlimb Impedance Ratios: Implications for Early Diagnosis of Uniand Bilateral, Upper and Lower Limb Lymphedema
Megan L. Steele, PhD, 1 Monika Janda, PhD, 1 Dimitrios Vagenas, PhD, 1 Leigh C. Ward, PhD, 2 Bruce H. Cornish, PhD, 1 Robyn Box, PhD, 3 Susan Gordon, PhD,4,5 Melanie Matthews, BPhysio (Hons), 4 Sally D. Poppitt, PhD, 6 Lindsay D. Plank, PhD, 7 Wilson Yip, MHSc, 6 Angela Rowan, MNutr, 8 Hildegard Reul-Hirche, DipPhty, 9 Andreas Obermair, MD,10 and Sandra C. Hayes, PhD1. Lymphatic Research Biology 2018
Background: Bioimpedance spectroscopy detects unilateral lymphedema if the ratio of extracellular ﬂuid (ECF) between arms or between legs is outside three standard deviations (SDs) of the normative mean. Detection of bilateral lymphedema, common after bilateral breast or gynaecological cancer, is complicated by the unavailability of an unaffected contralateral limb. The objectives of this work were to (1) present normative values for interarm, interleg, and arm-to-leg impedance ratios of ECF and ECF normalized to intracellular ﬂuid (ECF/ICF); (2) evaluate the inﬂuence of sex, age, and body mass index on ratios; and (3) describe the normal change in ratios within healthy individuals over time.
Methods: Data from ﬁve studies were combined to generate a normative data set (n=808) from which mean and SD were calculated for interarm, interleg, and arm-to-leg ratios of ECF and ECF/ICF. The inﬂuence of sex, age, and body mass index was evaluated using multiple linear regression, and normative change was calculated for participants with repeated measures by subtracting their lowest ratio from their highest ratio. Results: Mean (SD) interarm, interleg, dominant arm-to-leg, and nondominant arm-to-leg ratios were 0.987 (0.067), 1.005 (0.072), 1.129 (0.160), and 1.165 (0.174) for ECF ratios; and 0.957 (0.188), 1.024 (0.183), 1.194 (0.453), and 1.117(0.367) forECF/ICFratios, respectively. Arm-to-leg ratios were signiﬁcantly affected by sex, age, and body mass index. Mean normative change ranged from 7.2% to 14.7% for ECF ratios and from 14.7% to 67.1% for ECF/ICF ratios.
Conclusion: These ﬁndings provide the necessary platform for extending bioimpedance-based screening beyond unilateral lymphedema.