Microcomputed tomography versus plethysmometer and electronic caliper in the measurements of lymphedema in the hindlimb of mice.

Lymphedema affects 20% of women diagnosed with breast cancer. It is a pathology with no known cure. Animal models are essential to explore possible treatments to understand and potentially cure lymphedema. The rodent hindlimb lymphedema model is one of the most widely used. Different modalities have been used to measure lymphedema in the hindlimb of mice, and these are generally poorly assessed in terms of the interrater agreement; thus, there could be a risk of measuring bias and poor reproducibility. We examined the interrater agreement of µCT-scans, electronic caliper thickness of the paw and plethysmometer in the measurement of lymphedema in the hindlimb of mice. Three independent raters assessed 24 C57BL6 mice using these three modalities four times (week 1, 2, 4 and 8) with a total of 96 samples. The mean interrater differences were then calculated. The interrater agreement was highest in the µCT-scans, with an extremely low risk of measurement bias. The interrater agreement in the plethysmometer and electronic caliper was comparable with a low to moderate risk of measurement bias. The µCT-scanner should be used whenever possible. The electronic caliper should only be used if there is no µCT-scanner available. The plethysmometer should not be used in rodents of this size.