Durometry for the assessment of skin disease in systemic sclerosis.
OBJECTIVE
To examine the validity of a durometer to objectively measure skin hardness in systemic sclerosis (SSc), and to compare digital durometry with the modified Rodnan skin score (MRSS) and ultrasonography.


METHODS
Patients with SSc and healthy controls underwent durometry measurements in 3 assessments: a Latin square experiment to establish durometry's intra- and interobserver reliability compared with skin scoring (5 SSc, 1 control); a longitudinal cohort to assess sensitivity to change in skin hardness (13 SSc, 5 controls); and an ultrasound cohort to evaluate correlation between durometry, ultrasound-measured skin thickness, and clinical skin scoring (30 SSc, 12 controls).


RESULTS
Intraobserver reproducibility was higher for durometry than for clinical skin scoring (intraclass correlation coefficient [ICC] 0.97 versus 0.85), whereas interobserver reproducibility was similar (0.75 versus 0.73). Interobserver reproducibility of durometry was good for all body areas (ICC 0.61-0.85), but for skin scoring it was moderate in the legs (0.51) and poor in the abdomen (0.08), feet (0.09), and fingers (0.27). Durometry scores correlated with clinical skin scores (Latin square: r = 0.44, P = 0.03; longitudinal cohort: r = 0.81, P < 0.001) and ultrasound-measured skin thickness (hands: r = 0.58, forearms: r = 0.63, upper arms: r = 0.40; P < or = 0.001 for all). Uninvolved skin in patients with SSc was harder than skin from controls (mean +/- SD 23 +/- 7 durometer units [DU] versus 19 +/- 6 DU; P < 0.0001). Finally, there was a strong correlation between change in MRSS and change in durometry score (r = 0.77, P = 0.002).


CONCLUSIONS
Durometer-measured skin hardness correlates well with MRSS and ultrasound-measured skin thickness, provides greater reliability than MRSS, and is sensitive to changes in skin hardness over time. Durometry should be considered for use in clinical therapeutic SSc trials.
Kissin
Eugene Y
EY
Boston University School of Medicine, Boston, Massachusetts 02118, USA.
Schiller
Aileen M
AM
Gelbard
Rondi B
RB
Anderson
Jennifer J
JJ
Falanga
Vincent
V
Simms
Robert W
RW
Korn
Joseph H
JH
Merkel
Peter A
PA
D001132:Arm; D015331:Cohort Studies; D005385:Fingers; D006225:Hand; D006801:Humans; D015588:Observer Variation; D012016:Reference Values; D012595:Scleroderma, Systemic / Q000503:physiopathology*; D012680:Sensitivity and Specificity; D012867:Skin / Q000473:pathology*; D012871:Skin Diseases / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D012885:Skinfold Thickness