Background/Purpose: Skin manifestations of scleroderma involve the digits in nearly all patients. Assessment of change at the level of digital skin involvement is difficult. The Modified Rodnan Skin Score (MRSS) is the most commonly used assessment for quantifying skin involvement. Its use is limited to measuring thickness at only two locations: the dorsum of the third digit of each hand. Recently, the use of a durometer to measure finger hardness at these two sites provided the possibility of improved quantitative assessment of skin involvement.  The purpose of this study was to compare manual palpation and durometry as alternate methods of measuring finger involvement in scleroderma.

Methods: Fingertip pads of 30 patients with limited scleroderma (Scl cases), were compared with 30 age- and gender-matched controls without scleroderma. Skin hardness was assessed by manual palpation of the distal phalangeal palmar pad areas digits 1-5 bilaterally, using a scale of 0–3, with 0 indicating no involvement and 3 indicating extreme hardness. After calibration, durometry was performed in the same areas using a Rex 1600 Type 00 durometer rated on a scale of 0 (softest) to 100 (hardest). Two independent investigators recorded their findings on each patient in all digits using both methods. After 1 hour, Scl cases were remeasured by the same two investigators. Manual and durometry-based skin scores were obtained by averaging all digits for each assessment. Intra-class correlation (ICC) coefficients were used to assess differences in skin scores between investigators and repeatability.

Results: Mean age of cases and controls was 56 years (min: 30, max: 80) and 80% were female. There was a significant difference between the mean rating of all digits of Scl-cases and controls using either the manual (mean 1.5 vs 0.1; p<0.001) or the durometer method (mean 38 vs. 15; p<0.001). Between right and left hands, measurements for each finger were compared separately. Only manual ratings of the fifth digits were found be significantly different with right having a higher rating than left. Comparing each hand overall, both the manual durometer measurements showed that the left hand had significantly higher ratings than the right (manual: mean difference=0.19, p=0.008; durometer: mean difference=3.26, p=0.002). Intra-rater variability was low, as demonstrated by a high correlation in initial values recorded by individual raters and values recorded after one hour (ICC>0.90). Inter-rater variability was assessed comparing one main rater’s measurements of Scl-cases to other raters. All raters seemed to agree with the main rater (ICCs ≥0.69) for any finger. Coefficients did not change significantly from baseline to 1 hour assessment. Minimal detectable difference was smaller for durometry (11%) than for manual palpation (29%) indicating durometry may be able to detect smaller changes than manual rating.

Conclusion: Manual palpation and/or durometry performed on distal phalangeal palmar pads provided reproducible tools to assess skin hardness in fingers of Scl patients. Both have minimal inter- and intra-observer variability. Durometry may be able to detect smaller changes than manual palpation. It may have greater utility clinically and in clinical trials.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/fingertip-skin-hardness-in-limited-scleroderma-durometry-versus-manual-assessment/