Reproducibility and repeatability of the Myoton to quantify sclerotic chronic graft-versus-host disease

There is an urgent need for validated tools to measure sclerotic cutaneous chronic graft-versus-host disease (scGVHD). We examined the interobserver reproducibility within a session and intraobserver repeatability between sessions of the Myoton device for quantifying skin sclerosis in 36 adults with scGVHD. The Myoton was used to measure oscillation frequency and relaxation time of soft tissues at 7 bilateral sites (14 anatomic sites) by 2 study personnel at 2 study sessions. Agreement was measured using mean pairwise absolute difference (MPD), and reliability was measured using intraclass correlation coefficient (ICC). For each of the 2 Myoton parameters, the overall interobserver MPD was <5% of the average overall values and the interobserver ICC was >0.90 between the 2 observers, indicating excellent agreement and reliability within a measurement session. The median time between sessions 1 and 2 was 47.5 days. The overall normalized intraobserver MPD was <7% of the average overall values for each of the 2 Myoton parameters, reflecting good agreement between sessions. The intraobserver ICC for frequency and relaxation time parameters were 0.85 and 0.84, respectively, indicating good reliability between sessions. The reproducibility and repeatability of a bonus site selected at each study visit were similar to the standard 14 anatomic sites. However, no individual site was nearly as reproducible or repeatable as the overall Myoton measurements averaged across the patient. Our findings emphasize the utility of the Myoton for assessing skin properties in scGVHD with patient-level measurements.