SKIN THICKNESS SCORE IN SYSTEMIC-SCLEROSIS - AN ASSESSMENT OF INTEROBSERVER VARIABILITY IN 3 INDEPENDENT STUDIES

Objective. Using data from 3 independent studies, to quantify the inte robserver reliability of semiquantitative skin scoring methods (the or iginal and the modified Rodnan skin thickness scores) used to assess t he degree and extent of cutaneous thickening in systemic sclerosis (SS c). Method. Interobserver variability of the original Rodnan skin thic kness score method (cutaneous thickness assessed in 26 body surface ar eas using a 0-4 scale) was evaluated in one study. The modified Rodnan method (cutaneous thickness assessed in 17 body surface areas using a 0-3 scale) was evaluated in 2 studies. In all 3 studies, each patient 's skin thickness was assessed by 6 or 7 observers in a blinded fashio n. Results. The overall within patient standard deviations were not st atistically different in all 3 studies (5.4, 4.6 and 4.6) irrespective of the overall mean skin thickness scores (26.6,18.3 and 17.7). With the original Rodnan technique, the within patient standard deviation t ended to be higher in patients with higher skin thickness scores. In t he 2 studies which used the modified technique, no significant differe nces in within patient standard deviation were noted between high and low skin thickness scores. Conclusions. Three independent studies demo nstrate that the Rodnan skin thickness scoring techniques are reproduc ible among different observers (the within patient standard deviation being consistently about 5 units). Our data provide valuable informati on needed for sample size calculations for SSc trials in which skin th ickness score is an outcome variable.