Abstract

Intra-Rater Reliability and Agreement of the Indurometer When Used to Assess Mid-Calf Tissue Compressibility Among People Affected by Moderate to Severe Lymphedema in Bangladesh and Ethiopia

Janet Douglass, PhD,1 Hayley Mableson, PhD,1 Sarah Martindale, MPH,1 Jahirul Karim,2 ASM Sultan Mahmood, MPH,2 Fikre Hailekiros, MPH,3 and Louise Kelly-Hope, PhD1. Lymphatic Research Biology, 2019.

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 timepoints 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.

Main findings

• In Bangladesh, 146 people were included in the study but due to availability of the devices data could not be collected at baseline. In Ethiopia, 126 people were included and data were available at all time points. The study was conducted over 24 weeks and at final follow-up there was a retention rate of 82.6% in Bangladesh (n=133) and 81.8% in Ethiopia (n=103).
• The research teams in Bangladesh and Ethiopia all achieved ICC scores higher than 0.8 with most instances higher than 0.9, and this is similar to ICC scores for the same device when used at the same measurement point in healthy young people in Myanmar and Australia (range 0.906 [0.857–0.955]-0.942 [0.910–0.973]).
• In lymphedema, tissue compressibility scores should be interpreted in conjunction with other objective assessments such as lymphedema stage. In the very early fluid-rich stages, the tissue is soft and easily compressible and tonometry scores will be high. In the middle stages, the gradual build-up of fibrous tissues makes the tissue feel stiff and immobile. Adipose cells may also respond by accumulating and proliferating, and this fatty induration gives the tissue a spongy quality that rebounds immediately after compression. In later stages, hyperkeratosis and sclerosis of the skin will increase tissue stiffness further.
• Therefore, in early lymphedema when the swelling is very soft higher Indurometer scores can be expected and will decrease if the fluid is removed. In later stages when the tissue has become fibrotic, lower scores can be expected and if effective treatment softens the tissues then Indurometer scores will increase. Any assessment of tissue compressibility or stiffness should also consider known moderating factors such as age, gender, and body composition