European multicentre study to define disease activity criteria for systemic sclerosis. II. Identification of disease activity variables and development of preliminary activity indexes

Objective - To develop criteria for disease activity in systemic sclerosis (SSc) that are valid, reliable, and easy to use. Methods - Investigators from 19 European centres completed a standardised clinical chart for a consecutive number of patients with SSc. Three protocol management members blindly evaluated each chart and assigned a disease activity score on a semiquantitative scale of 0-10. Two of them, in addition, gave a blinded, qualitative evaluation of disease activity ("inactive to moderately active" or "active to very active" disease). Both these evaluations were found to be reliable. A final disease activity score and qualitative evaluation of disease activity were arrived at by consensus for each patient; the former represented the gold standard for subsequent analyses. The correlations between individual items in the chart and this gold standard were then analysed. Results - A total of 290 patients with SSc (117 with diffuse SSc (dSSc) and 173 with limited SSc (lSSc)) were enrolled in the study. The items (including Δ-factors that is, worsening according to the patient report) that were found to correlate with the gold standard on multiple regression were used to construct three separate 10-point indices of disease activity: (a) Δ-cardiopulmonary (4.0), Δ-skin (3.0), Δ-vascular (2.0), and Δ-articular/muscular (1.0) for patients with dSSc; (b) Δ-skin (2.5), erythrocyte sedimentation rate (ESR) >30 mm/1st h (2.5), Δ-cardiopulmonary (1.5), Δ-vascular (1.0), arthritis (1.0), hypocomplementaemia (1.0), and scleredema (0.5) for lSSc; (c) Δ-cardiopulmonary (2.0), Δ-skin (2.0), ESR >30 mm/1st h (1.5), total skin score >20 (1.0), hypocomplementaemia (1.0), scleredema (0.5), digital necrosis (0.5), Δ-vascular (0.5), arthritis (0.5), TLCO