Lower limb lymphedema: reliability of four non-imaging measurement modalities

To assess intra- and inter-rater reliability of four non-imaging measuring modalities in lower limb lymphedema (LLL): perometry (PM), circumferential tape measurements (CTMs), bioimpedance spectroscopy (BIS), and tissue dielectric constant (TDC).

In this study, 51 adults with LLL were assessed by two physiotherapists. Measurements were completed within 45 min in alternating order. Reliability was evaluated using intraclass correlation coefficients (ICC_2,1), standard error of measurement (SEM), 95% confidence limits for SEM (SEM₉₅), smallest real difference (SRD%), and Bland-Altman analysis.

PM, CTM, and BIS demonstrated excellent reliability (ICC_2,1 ≥ 0.900) while TDC showed good to excellent reliability (ICC_2,1: 0.761-0.933). SEM₉₅ was lowest for PM (263-282 mL), with greater error for CTM (505-767 mL), BIS (6.0-7.2 lymphedema-index (L-Dex score) units), and TDC (3.6-7.8%PWC). SRD values demonstrated a required change of 4% with PM, 7-11% with CTM, 8-10 L-Dex points with BIS, and 12.4-26.2% with TDC to exceed measurement error.

PM, CTM, and BIS provide reliable LLL assessment. TDC showed greatest site-dependent variability, necessitating cautious interpretation. Our findings support PM as the most precise volume measure, CTM as a practical alternative, and BIS and TDC as complementary tools for quantifying extracellular and localized tissue fluid.