Portable infrared imaging for longitudinal limb volume monitoring in patients with lymphatic filariasis

Background The Global Programme to Eliminate Lymphatic Filariasis (LF) emphasizes hygiene, exercise, and other measures to reduce morbidity and disability related to LF. We recently reported that a portable, three-dimensional, infrared imaging system (3DIS) provides accurate limb volume measurements in patients with filarial lymphedema. To assess the practical utility of repeated 3DIS measurements for longitudinal lymphedema management, we examined intraday and day-to-day leg volume changes in adults with filarial lymphedema in southern Sri Lanka. Methodology and principal findings We assessed 41 participants with lower extremity lymphedema (stages 1–6) in their homes in the mornings (6:00–9:00 AM) and afternoons (2:00–6:00 PM) of three days within one calendar week. Two examiners performed replicate 3DIS volume measurements at each visit. Median coefficient of variation among replicate volume measurements was 1.7% (IQR 1.1% - 2.3%) for left legs and 2.2% (IQR 1.6% - 2.8%) for right legs. Median intraday volume increase was 3.0%. Range among daily volume measurements tended to be lower for afternoon measurements (median 2.25%, IQR 1.4%– 5.4%) than for morning measurements (median 3.0%, IQR 1.4% - 8.4%). Conclusions and significance Limb volume measurements by 3DIS are accurate and reproducible, and this technique is feasible for use in patients’ homes. We have developed practical suggestions for optimal outcomes with 3DIS. Duplicate measurements should be performed and repeat assessments should be done at approximately the same time of day to minimize bias. Duplicate measures that vary by more than 8% should prompt review of scanning technique with a repeat measurement. With proper training and attention to technique, 3DIS can be a valuable tool for healthcare workers who work with lymphedema patients.
Author summary Morbidity Management and Disability Prevention (MMDP) is a critical but neglected component of the Global Programme to Eliminate Lymphatic Filariasis. Lack of infrastructure, trained practitioners, political will, and resources are challenges to effective implementation of MMDP services. This is compounded by the paucity of treatment options for limb lymphedema. Currently daily washing, elevation, and exercise are the only therapy available to most patients with filarial limb lymphedema, and new treatments are sorely needed. We previously reported that portable three-dimensional infrared imaging provides rapid, accurate, and reproducible limb measurements in patients with filarial lymphedema. Here, we show that similarly accurate and reproducible limb measurements are possible outside the clinic (in or outside patients’ homes). Using this technique we quantify how much limb volume varies from day to day and during the day for patients with filarial lymphedema, and provide recommendations for the optimal use of this tool in longitudinal monitoring of limb volume in research or in the clinic.