Interchangeability of two electrode placement protocols used by bioimpedance spectroscopy devices in the detection of breast cancer-related lymphedema

Background: Bioimpedance spectroscopy (BIS) devices are routinely used in the assessment of breast cancer-related lymphedema (BCRL). The equipotential electrode placement is a commonly used protocol for the assessment of BCRL. However, the sternal notch electrode placement protocol is also in use. Whether these two protocols are interchangeable is not known. Methods and Results: Ethical approval was received from the institutional ethics committee at Tata Memorial Hospital, India. BIS measurements (whole-body right side and affected and unaffected arms) of 100 women with or at risk of BCRL were measured using equipotential and sternal notch protocols. Resistance at zero frequency (R0) was determined, and agreement of the absolute R0 values and the R0 ratio (unaffected/affected) between protocols was evaluated (Bland-Altman analysis and Passing-Bablok regression analysis). Mean absolute differences between protocols were very small for whole-body right side, affected arm, unaffected arm, and the interarm ratio at 0.23 ohms (95% confidence interval [CI]: -3.8 to 4.3), -5.7 ohms (95% CI: -7.5 to -3.9), -9.09 ohms (95% CI: -11.4 to -6.8), and -0.008 ohms (95% CI: -0.02 to 0.001), respectively. Limits of agreement (two standard deviation) between protocols were narrow for whole-body right side, affected arm, unaffected arm, and interarm ratio without any systematic or proportional differences for whole-body right side and the interarm ratio (5.8% to -5.6%, 3.7% to -7.4%, 3.5% to -8.2%, and 5.8% to -5.6%, respectively). Conclusion: The equipotential and sternal notch protocols could be used interchangeably in BCRL assessment. The Clinical Trial Registration number: CTRI/2017/12/010762.