Intrarater Reliability of Tonometry and Bioimpedance Spectroscopy to Measure Tissue Compressibility and Extracellular Fluid in the Legs of Healthy Young People in Australia and Myanmar

Background: Measurements of tissue compressibility and extracellular fluid (ECF) are used to monitor progression of lymphedema, a chronic swelling of the subcutaneous tissue. Later stages of lymphedema are characterized by fibrotic induration in the subcutis and hyperkeratosis of the skin. Several devices are available to measure these changes, but previous reliability and validity studies have been conducted primarily on adult women with unilateral arm lymphedema using contralateral limbs as controls. To date, no studies have included either adolescents or measurement of leg tissue. Methods and Results: An intrarater reliability study was conducted to compare three devices measuring skin and subcutaneous tissue compressibility; a mechanical Tonometer, a digital Indurometer, and a SkinFibroMeter. ECF loads were measured using bioimpedance spectroscopy (BIS). Two populations of tropical-dwelling young people were included; Australian residents in North Queensland aged 8-21 years (n = 34) and people aged 10-21 years residing in Central Myanmar (n = 38). Neither cohort had any clinical sign of lymphedema or other leg abnormality. The mechanical Tonometer and the digital Indurometer had excellent intraclass correlation coefficient (ICC) scores between 0.792 (95% CI 0.055-0.901) and 0.964 (95% CI 0.945-0.984) and the SkinFibroMeter had good to excellent reliability with ICC scores of between 0.565 (95% CI 0.384-0.747) and 0.877 (95% CI 0.815-0.840). BIS exhibited the highest reliability with ICC scores approaching 1.0. Conclusions: These results support the reliable use of tonometry and BIS to assess tissue compressibility and ECF loads in the legs of adolescent populations in developed and developing tropical countries.