Bioimpedance testing for lymphedema
Breast cancer-related lymphedema (BCRL) is a chronic, debilitating disorder that is frequently misdiagnosed, treated too late or not treated at all. Being able to quantitively follow it or predict its onset or severity would be clinically useful. Bioimpedance is one method of obtaining scores that may prove predictive with followup and over time.
The L-Dex XCA is a bioimpedance analyzer designed to assist in the clinical assessment of unilateral lymphedema of the arm. The L-Dex XCA utilizes a simple linear scale called the L-Dex (lymphedema index). The L-Dex ranges from -10 to +10 and defines the normal range of L-Dex values for a patient without lymphedema. The presence or absence of lymphedema is assessed by comparing the patient’s L-Dex to this range.
ImpediMed LDex™ U400 (ImpediMed Limited, San Diego, CA) was approved for marketing by the U.S. Food and Drug Administration (FDA) through the 510(k) process in 2008. Thus, the manufacturer was not required to provide the evidence of clinical efficacy that is necessary to support a premarket approval (PMA). According to the FDA clearance letter, the device is “to aid in the clinical assessment of unilateral lymphedema of the arm in women.” The FDA labeling states that the device is “not intended to diagnose or predict lymphedema of an extremity.” One grequnetly quoted study to support L-DEX is Stout Gergich et al (2008) is a report of a case-control study but ti used a different technology, perometry, in the diagnosis and management of subclinical lymphedema in patients with early-stage breast cancer. The article states that “further research is needed” to validate bioimpedance in the context of a surveillance tool.
There are no unequivocally supportive guidelines.
The National Lymphedema Network position statement, Screening and Measurement for Early Detection of Breast Cancer Related Lymphedema, updated April 2011, states that circumferential tape measurements are acceptable means of measuring limb volume. The current position statement states “bioelectrical spectroscopy (BIS) or infrared perometry are suggested as alternative or adjunctive methods to circumferential measurement.”
A technology assessment of the diagnosis and management of secondary lymphedema prepared for the Agency for Healthcare Research and Quality (Oremus et al, 2010) concluded: “There is consistent evidence to indicate that lymphedema can be reliably measured using circumferential measures or volume displacement … There is too little evidence to draw conclusions about the reliability of other tests such as tonometry, ultrasound, lymphoscintigraphy, or bioimpedance.”
The Northern Ireland CREST Committee guidelines for lymphedema (2008) recommend circumferential limb volume measurement for assessing limb volume. Bioimpedance measurement is described as promising, noting that it should be considered over the next 5 years. Presumably, an updates statemetns will soon be issued.
The National Cancer Institute Physician Data Query (PDQ) on lymphedema (NCI, 2011) states that circumferential upper-extremity measurement is the most widely used method to diagnose upper-extremity lymphedema. Bioimpedance is listed among several other options for evaluating limb volume. The PDQ also stated that a study comparing various methods of assessing upper-limb lymphedema did not show any superiority of any one method; for support, the PDQ cited a study by Ridner, et al. (2007) comparing circumferential limb measurements to bioimpedance and perometry.
On the balance, there is some support in guideliens for the concept of testing for the risk of lymphedema over time, but specifically bioimpedance appears not to be well supported.
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