Validity, reliability, and feasibility of durometer measurements of scleroderma skin disease in a multicenter treatment trial.
OBJECTIVE
To determine the validity, reliability, and feasibility of durometer measurements of skin hardness as an outcome measure in clinical trials of scleroderma.


METHODS
Skin hardness was measured during a multicenter treatment trial for scleroderma using handheld digital durometers with a continuous scale. Skin thickness was measured by modified Rodnan skin score (MRSS). Other outcome data collected included the Scleroderma Health Assessment Questionnaire. In a reliability exercise in advance of the trial, 9 investigators examined the same 5 scleroderma patients by MRSS and durometry.


RESULTS
Forty-three patients with early diffuse cutaneous systemic sclerosis were studied at 11 international centers (mean age 49 years [range 24-76], median disease duration 6.4 months [range 0.3-23], and median baseline MRSS 22 [range 11-38]). The reliability of durometer measurements was excellent, with high interobserver intraclass correlation coefficients (ICCs) (0.82-0.92), and each result was greater than the corresponding skin site ICCs for MRSS (0.54-0.85). Baseline durometer scores correlated well with MRSS (r = 0.69, P < 0.0001), patient self-assessments of skin disease (r = 0.69, P < 0.0001), and Health Assessment Questionnaire (HAQ) disability scores (r = 0.34, P = 0.03). Change in durometer scores correlated with change in MRSS (r = 0.70, P < 0.0001), change in patient self-assessments of skin disease (r = 0.52, P = 0.003), and change in HAQ disability scores (r = 0.42, P = 0.017). The effect size was greater for durometry than for MRSS or patient self-assessment.


CONCLUSIONS
Durometer measurements of skin hardness in patients with scleroderma are reliable, simple, accurate, demonstrate good sensitivity to change compared with traditional skin scoring, and reflect patients' self-assessments of their disease. Durometer measurements are valid, objective, and scalable, and should be considered for use as a complementary outcome measure to skin scoring in clinical trials of scleroderma.
Merkel
Peter A
PA
Boston University School of Medicine, Boston, MA 02118, USA. pmerkel@bu.edu
Silliman
Nancy P
NP
Denton
Christopher P
CP
Furst
Daniel E
DE
Khanna
Dinesh
D
Emery
Paul
P
Hsu
Vivien M
VM
Streisand
James B
JB
Polisson
Richard P
RP
Akesson
Anita
A
Coppock
John
J
van den Hoogen
Frank
F
Herrick
Ariane
A
Mayes
Maureen D
MD
Veale
Douglas
D
Seibold
James R
JR
Black
Carol M
CM
Korn
Joseph H
JH
D000328:Adult; D000368:Aged; D004311:Double-Blind Method; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D015203:Reproducibility of Results; D012595:Scleroderma, Systemic / Q000473:pathology*; D012680:Sensitivity and Specificity; D012867:Skin / Q000473:pathology*; D012885:Skinfold Thickness; D011795:Surveys and Questionnaires