Reliability of the Inverse Water Volumetry Method to Measure the Volume of the Upper Limb

Background: Lymphedema of the upper extremity is a common side effect of lymph node dissection or irradiation of the axilla. Several techniques are being applied in order to examine the presence and severity of lymphedema. Measurement of circumference of the upper extremity is most frequently performed. An alternative is the water-displacement method. The aim of this study was to determine the reliability and the reproducibility of the Inverse Water Volumetry apparatus (IWV-apparatus) for the measurement of arm volumes. Patients and Methods: The IWV-apparatus is based on the water-displacement method. Measurements were performed by three breast cancer nurse practitioners on ten healthy volunteers in three weekly sessions. Results: The intra-class correlation coefficient, defined as the ratio of the subject component to the total variance, equaled 0.99. The reliability index is calculated as 0.14kg. This indicates that only changes in a patient's arm volume measurement of more than 0.14kg would represent a true change in arm volume, which is about 6% of the mean arm volume of 2.3kg. Conclusion: The IWV-apparatus proved to be a reliable and reproducible method to measure arm volume.