Validation of the inverse water volumetry method: a new gold standard for arm volume measurements

Background No consensus exists with respect to a commonly accepted and standardized method for measuring arm volumes in patients with lymphedema. Knowing the exact volume in (potential) lymphedemic arms and comparing this volume with healthy arms is important to detect the first signs of lymphedema and to study the effects of treatment. Methods A new apparatus, based upon the principle of measuring shortness of water, was developed to measure arm volumes. This measuring-method, inverse water volumetry, was prospectively validated in patients, suffering from lymphedema after complete or partial mastectomy for primary breast cancer. Healthy and lymphedemic arm were measured 3 times: twice by nurse A (A1 and A2) and once by nurse B (B). Subsequently, these differences in volumes were compared with differences in volumes obtained by the Herpertz method, which is based upon circumferential measurement. Results In every patient at every occasion volume of the lymphedemic arm was bigger than the corresponding volume of the control arm. Mean volumes of healthy arms were 3958(A1) 3966(A2) and 3961(B) ml respectively. Mean volumes of lymphedemic arms were 4721(A1), 4752(A2) and 4773(B) ml respectively, volume B being significantly different from volume A1. Volume difference of edemic arms minus control arms was not significant between measurements (A1 vs. A2 and A1 vs. B, respectively), while this difference was significant (A1 vs. B) using the Herpertz method. Conclusion Inverse water volumetry is an easy measuring device with a high inter- and intra-observer agreement. The small but significant volume increase of lymphedemic arms in time compared to the constant volumes of control arms is as well indicative for the accuracy of the method as for the volume of lymphedemic arms to increase when no therapeutic garment is carried.