BACKGROUND Bioimpedance spectroscopy (BIS) assesses resistance (impedance) to the flow of an electrical current. Through the measurement of impedance to currents at low (R0) and high (Rinf) frequencies, extracellular fluid (ECF) and total body fluid (TBF) can be measured, respectively, and intracellular fluid (Ri = ICF) subsequently extrapolated (TBW = ECF + ICF). Measuring bilateral upper-limb or lower-limb secondary lymphoedema following cancer is complicated by the unavailability of a comparable, unaffected limb. Availability of normative BIS data for all 4 limb segments would enable an extension of BIS in the diagnosis of bilateral upper-, as well as lower-limb lymphoedema. The purpose of this study was to describe normative arm to leg, arm to arm and leg to leg impedance ratios and to determine optimal cut-off thresholds for diagnosing lymphoedema by testing the accuracy of cut-offs based on normative means plus or minus 0.5 to 3 SDs to diagnose known cases of lymphoedema
