Evaluation of upper limb lymphoedema and diagnostic accuracy of bioimpedance spectroscopy. A comprehensive validation in a Brazilian population

Lymphoedema is a complication of breast cancer treatment. Its early diagnosis is related to a good prognosis for lymphoedema treatment. The bioimpedance spectroscopy (BIS) evaluates changes in extracellular fluid. The objective of our study was to evaluate the validity, agreement and accuracy of BIS in the diagnosis of breast cancer-related lymphoedema in a Brazilian population. This is a prospective, cross-sectional study of a convenience sample of 462 women who underwent surgical treatment for breast cancer (mastectomy or breast-conserving treatment). The validity, agreement and accuracy were performed comparing BIS (lymphoedema index (L-DEX) ≥ 6.5 or 10) with volumetry by water displacement, which is the gold standard for evaluating lymphoedema. Receiver operating characteristic curve was performed. Additionally, other methods like perimetry and indirect volumetry of the upper limbs were compared with water displacement volumetry (direct volumetry), and the BIS were compared with subjective evaluation. Considering L-DEX ≥ 10 the sensitivity of the BIS was 44.1%, specificity 95.4%, positive predictive value (PPV) was 70.7%, negative predictive value (NPV) was 87% and kappa was 0.459. The BIS with L-DEX ≥ 6.5, the sensitivity, specificity, PPV, NPV and kappa were 57%, 88.5%, 55.8%, 89% and 0.452, respectively. Area under curve was 0.724 and a possible cut-off point of L-DEX ≥ 7.35 with sensitivity of 57%, specificity of 90.7% and kappa value = 0.489. Although BIS was significantly associated with the subjective evaluation of lymphoedema, it showed low sensitivity and agreement and moderate correlation when used as a method for diagnosing the condition. Thus, it is not the most valid method for evaluating lymphoedema. In addition, it was not the most accurate method when compared with other objective evaluation tools. Public health resources are scarce and must be used consciously. The knowledge that BIS is not a more accurate method than other, lower-cost instruments allows for better targeting of these resources.