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

• The Myoton had excellent inter-observer and good intra-observer agreement.

• A bonus site selected for severe involvement had similar inter- and intra-observer agreement as standard anatomic sites.

Validated tools to measure sclerotic cutaneous chronic Graft-versus-Host Disease (scGVHD) is an urgent need. We examined the inter-observer reproducibility within a session and intra-observer 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 two study personnel at two study sessions. Agreement was measured with mean pairwise absolute difference (MPD), and reliability was measured with intraclass correlation coefficient (ICC). For each of the two Myoton parameters, the overall inter-observer MPD was less than 5% of the average overall values and the inter-observer ICC was greater than 0.90 between the two observers, indicating excellent agreement and reliability within a measurement session. The median time between session 1 and session 2 was 47.5 days. The overall normalized intra-observer MPD was less than 7% of the average overall values for each of the two Myoton parameters, reflecting good agreement between sessions. The intra-observer ICC for frequency and relaxation time parameters were 0.85 and 0.84, respectively, indicating good reliability between sessions. Reproducibility and repeatability of a bonus site selected at each study visit was 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.