Background: Lymphedema is a chronic skin disease that induces tissue fibrosis (stiffness). Tissue tonometry has been used to assess skin and tissue compressibility in lymphedema, primarily in research on arm lymphedema after breast cancer. A digital tonometer, the Indurometer (Flinders and SA Biomedical Engineering, Australia), has shown excellent intra-rater reliability in young healthy people in Australia and Myanmar and was able to detect covert changes in young, asymptomatic Myanmar people infected with lymphatic filariasis. It has not been tested in overt lower-limb lymphedema. Methods and Results: The Indurometer was used in a cluster randomized trial in Bangladesh and Ethiopia to measure tissue compressibility among adults affected by moderate to severe lymphatic filariasis- or podoconiosis-related leg lymphedema. The study compared different self-care intervention and after baseline there were follow-ups at 4, 12, and 24 weeks. Three consecutive Indurometer scores were collected by two data collection teams in each country at the mid-calf of each leg. Indurometer scores were available for three time-points in Bangladesh and four time-points in Ethiopia. An intra-class correlation coefficient (ICC) was calculated for each data collection team, and a coefficient of variation (CV) was used to assess measurement agreement in moderate and severe stages of lymphedema. The intra-rater reliability among local research assistants was good to excellent in both countries at all time-points (ICC range 0.829 [95% confidence interval; CI 0.730-0.896]-0.992 [95% CI 0.989-0.995]). In Bangladesh, agreement between measures was highest among unaffected legs (range 16%-22%) and lowest in severe lymphedema (range 19%-39%). CV scores in Ethiopia showed no distinct pattern for lymphedema stage (range 15%-32%). Conclusion: The Indurometer is an inexpensive and easy-to-use device to assess skin and tissue compressibility and should be considered in clinical research on lower-limb lymphedema.
Keywords: lower limb; lymphatic filariasis; lymphedema; podoconiosis; reliability; tissue tonometry.