Durometry as an alternative tool to the modified Rodnan’s skin score in the assessment of diffuse systemic sclerosis patients: a cross-sectional study

Abstract

Background The reproducibility and reliability of the modified Rodnan’s Skin Score (mRSS) are debated due to investigator-related subjectivity. Here, we evaluate if durometry correlates with mRSS in patients with diffuse systemic sclerosis (SSc). Methods This cross-sectional study was conducted from December 2018 to June 2019, including 58 diffuse SSc patients. Two certified researchers, blind to each other’s scores, performed the mRSS, followed by durometry at 17 predefined skin sites. For durometry and mRSS, individual scores per skin site were registered. Durometry and mRSS results measured by each researcher, as well as scores from different researchers, were compared. Skin thickness measurements from forearm skin biopsies were available in a subset of the patients, for comparisons. Statistical analyses included Cohen’s Kappa Coefficient, Intraclass Correlation Coefficient, Kendall’s Coefficient and Spearman’s test. Results Mean (standard deviation, SD) patient age was 44.8 (12.9) years, and 88% were female. Inter-rater agreement varied from 0.88 to 0.99 (Intraclass correlation coefficient) for durometry, and 0.54 to 0.79 (Cohen’s Kappa coefficient) for mRSS, according to the specific evaluated sites. When data were compared with skin thickness assessed in forearm biopsies, durometry correlated better with skin thickness than mRSS. Conclusion Durometry may be considered as an alternative method to quantify skin involvement in patients with diffuse SSc. The strong inter-rater agreement suggests that the method may be useful for the assessment of patients by multiple researchers, as in clinical trials.

Skin involvement in early diffuse cutaneous systemic sclerosis: an unmet clinical need

“…As a measure of skin hardness, durometry has long been advocated as a possible outcome measure in clinical trials of early dcSSc 69 , but not widely adopted. However, in 2020 durometry was revisited 70 , and it deserves further investigation, including in longitudinal studies with examination of sensitivity to change. A durometer is hand-held, portable and relatively easy to use, making durometry a potentially useful additional outcome measure in multicentre studies.…”

Systemic sclerosis in adults. Part II: management and therapeutics

“…Durometry is an easy-to-use option, with demonstrated reliability and accuracy in SSc; correlating well with mRSS, ultrasound-measured skin thickness and skin biopsies. [7][8][9][10] Unlike durometers, which evaluate skin hardness through resistance to indentation, cutometers assess skin hardness through resistance to controlled suction. Cutometer measurements correlate reasonably well with the mRSS, 11 and newer devices have been developed more recently to lessen the potential for interobserver technique variability.…”

Use of a novel Indentometer to evaluate skin induration in localized scleroderma and psoriasis vulgaris

“…Results are obtained in Durometry units, and the lower numbers indicate less resistance and softer materials. [2][3][4] The Indentometer IDM 800 (Courage and Khazaka, Cologne, Germany) and the SkinFibroMeter (Delfin Technologies, Finland) are newer and little known to researchers. 2 Separately, both devices were applied successfully to evaluate the lymphedema of the lower limb.…”

“…The Durometer (Rex Gauge, IL, USA) is the international standard for the hardness measurement of rubber, plastic, and other non‐metallic materials and was the first instrument applied to measure skin hardness. Results are obtained in Durometry units, and the lower numbers indicate less resistance and softer materials 2–4 …”

“…Results are obtained in Durometry units, and the lower numbers indicate less resistance and softer materials. 2 , 3 , 4 …”