Our study “Preoperative Assessment Enables the Early Detection and Successful Treatment of Lymphedema” used infrared technology to measure limb volume for screening and diagnosis of lymphedema.1 The Perometer device is used routinely in research related to lymphedema diagnosis and management. Limb volume change over time can be tracked with a high degree of accuracy using the Perometer. Many trials have been conducted to qualify it as a sensitive, reliable tool.2 Our study was the first to use this measurement tool in a prospective manner to diagnose subclinical swelling. We defined subclinical lymphedema as >3% change in limb volume as compared to the baseline, preoperative limb volume with consideration for the contralateral limb. The Perometer device is sensitive enough to capture this slight change in limb volume, although it occurs before clinical signs of swelling are apparent. Because the Perometer is not an invasive device, there is no requirement for the FDA to approve it.
The multifrequency bioimpedance unit is a new measurement technology that is valid to measure clinically apparent lymphedema and to quantify change over time.3, 4 Prospective studies using the bioimpedance unit, however, have not been conducted to demonstrate its efficacy in detecting limb volume changes consistent with subclinical lymphedema at the threshold that we have demonstrated can be captured with the Perometer (3%). Box et al conducted a prospective surveillance program and found that the multifrequency bioimpedance unit was not sensitive enough to capture 50% of the patients in her cohort who developed lymphedema.5 They concluded that the device was not sensitive enough to detect the earliest clinical changes in the limb. This could be associated with several limitations of the device, including; the loss of sensitivity the device has when the patient is in an altered state of hydration, has not voided their bladder before measurement, or has not lain supine for 10 minutes before measurement. Each of these confounding factors may have precluded the device from being able to capture limb volume change at such a sensitive threshold of 3%.
Based on our study, the Perometer was effectively able to detect a minimum 3% limb volume change when a preoperative measurement was taken and patients were monitored at regular intervals overtime. This enabled early diagnosis and treatment of lymphedema. Further research should be conducted using the Perometer and the multi-frequency bioimpedance unit not only for concurrent validity in monitoring volume change over time, but to study the sensitivity of the measurement device for early detection.