Diagnostic accuracy of bioimpedance spectroscopy in patients with lymphedema: A retrospective cohort analysis

Evelyn S. Qin, Mindy J. Bowen, Wei F. Chen. Journal of Plastic, Reconstructive & Aesthetic Surgery 2018

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Diagnostic accuracy of bioimpedance spectroscopy in patients with lymphedema: A retrospective cohort analysis

Evelyn S. Qin, Mindy J. Bowen, Wei F. Chen. Journal of Plastic, Reconstructive & Aesthetic Surgery 2018

Summary

Background: Bioimpedance spectroscopy (BIS) is used by healthcare specialists to diagnose lymphedema. BIS measures limb fluid content by assessing tissue resistance to the flow of electric current. However, there is debate regarding the validity of BIS in diagnosing early lymphedema. Indocyanine green (ICG) lymphography has been established as the most accurate diagnostic modality to date for lymphedema diagnosis. In this retrospective study, we test the sensitivity, specificity, and diagnostic accuracy of BIS in diagnosing lymphedema by referencing its results with ICG lymphography.

Methods: Patients presented to the University of Iowa Lymphedema Center from 2015 to 2017 were evaluated with a standardized protocol that included history and physical examination, a validated lymphedema-specific quality-of-life assessment (LYMQOL), circumference –measurement-based index, BIS, and ICG lymphography. Diagnostic accuracy of BIS was assessed using ICG lymphography as a reference test.

Results: Fifty-eight patients had positive ICG lymphography results, which confirmed the diagnosis of lymphedema. ICG lymphographic findings consistently correlated with clinical examination, LYMQOL evaluation, and lymphedema indices. By contrast, BIS demonstrated a false-negative rate of 36% – 21 out of 58 patients had normal BIS readings, but a positive ICG lymphography result. The 21 false-negative results occurred in patients with early-stage disease. Sensitivity and specificity for BIS were 0.64 and 1, respectively. Conclusion: BIS carries an excessively high rate of false-negative results to be dependably used as a diagnostic modality for lymphedema. ICG lymphography highly correlates with other tracking modalities, and it remains the most reliable tool for diagnosing lymphedema.

Main findings

  • This study used both BIS and ICG lymphography to diagnose lymphoedema. It also used the validated lymphedema specific quality of life assessment (LMQOL) that assessed symptom severity and degree of lymphoedema disability.
  • The 62 patients comprised 58 (93%) women and 4 (7%) men, with average body mass index (BMI) of 29 ± 6.2 kg/m2 (Table 3). Thirty-six (58%) had UEL, 26 (42%) had LEL, 10 (16%) had primary lymphedema, and 52 (84%) had secondary lymphedema.
  • Of the patients with secondary lymphedema, 35 (67%) were associated with breast cancer, 9 (17%) gynecological cancer, 8 (15%) from other causes (e.g., prostate cancer, melanoma, and filariasis). Twenty-one (34%) of the individuals had early (Campisi stageI/II) disease, 19 (30%) had intermediate (Campisi stage III) disease, and 22 (36%) had late (Campisi stage IV/V) disease. Interestingly, of the patients with early Campisi stage disease, 7 had ICG severity IV/V.
  • When using 3SD above a normative mean and ICG lymphography as the reference, 21 of 58 patients had normal BIS readings and positive ICG results (i.e., false-negative rate of 36%). The same findings were seen using BIS L-dex >10 as the cut off.
  • The ICG lymphographic findings consistently correlated with clinical examination, LYMQOL assessment, and lymphedema indices. All four individuals with negative ICG lymphography results had negative BIS readings. Sensitivity and specificity of BIS were 0.64 and 1 at 3SD and 0.72 and 1 at 2SD, respectively. Negative likelihood ratio was 0.36 at 3SD and 0.28 at 2SD. Twenty patients with false-negative BIS results had mild-to intermediate Campisi severity (stage Ib to III) – only one presented with late-stage disease. When using 2SD as the cut off, 16 of 58 patients had normal BIS readings and positive ICG results (false-negative rate of 28%).
  • This study suggests because BIS measures ECF in a whole limb by comparing with the contralateral whole limb, early, localized changes may not be detected.
  • The authors believe the strength of BIS is its ability to measure values over time rather than in single instances. BIS measurements should be taken longitudinally to trend lymphatic fluid levels such as after lymphatic surgery in patients with lymphedema to monitor treatment efficacy.
  • BIS should not be the sole assessment tool for lymphedema diagnosis but is most efficacious when combined with other tools.
  • The study is limited by assuming that the medical records were accurate and that the BIS procedure was performed correctly.