Reference values of bioelectrical impedance analysis for detecting breast cancer-related lymphedema

Secondary lymphedema is a chronic debilitating lifelong complication and early diagnosis is crucial. The Inbody 720, which is widely used, has no universal index of diagnostic criteria for test results. We aim to determine the normal range, cutoff values, and mean + standard deviation values of extracellular fluid (ECF) and the single frequency bioimpedance (SFBIA) ratios for the diagnosis of lymphedema and suggest the usefulness of these values for detecting lymphedema. Seventy patients with unilateral breast cancer-related lymphedema and 643 healthy subjects were enrolled. All patients with breast cancer underwent surgeries with dissection of lymph nodes. We analyzed the ECF volume, SFBIA at 1- and 5-kHz frequencies using Inbody 720. There were significant differences between patients with BCRL and healthy controls. The optimal cutoff values for ECF ratios were 1.010 for both the dominant and non-dominant arms. At 1 kHz, the cutoff values of SFBIA were 1.050 and 1.046, and at 5 kHz, those were 1.070 and 1.030 for the dominant and non-dominant affected arms, respectively. The mean + 2SD values for ECF ratio were 1.018 and 1.020 and at 1 kHz, the mean + 2SD values of SFBIA were 1.144 and 1.0135 and at 5 kHz, the cutoff values of SFBIA were 1.141 and 1.124 for the dominant and non-dominant affected arms, respectively. The mean + 3SD values for ECF ratio were 1.026 and 1.030 and at 1 kHz, the mean + 3SD values of SFBIA were 1.206 and 1.203 and at 5 kHz, those were 1.201 and 1.187 for the arms, respectively. The cutoff, mean + 2SD, and mean + 3SD values were applied to 70 patients with unilateral BCRL. When the cutoff values were applied, a higher proportion of BCRL patients were included. When these figures were applied to the patient group, the cutoff values included a higher proportion of patients with lymphedema. Further studies are needed to investigate whether bioimpedance analysis can accurately predict the development of lymphedema.