L. Czirják

Skin thickening is a characteristic feature of SSc. More extensive skin involvement coincides with more severe internal organ manifestation(s), poor prognosis and increased disability, at least in the early phase of the diffuse cutaneous scleroderma subset. The fully validated, feasible method ('gold standard') for measuring the dermal skin thickness is the modified Rodnan skin score (mRSS). The responsiveness of mRSS was somewhat modest in clinical trials, and a careful teaching process is necessary. Parallel method(s) for measuring skin thickness need to be used in the future. Ultrasound (US) measurement of the dermis with a 20-30 MHz probe is a valid, reproducible and responsive method in patients with dcSSc. However, US is time-consuming and requires a training process. Of the mechanical instruments available, only the durometer, which measures the hardness of skin, has been validated. The inter- and intra-observer reproducibility and sensitivity to change of durometry were good, and correlated with mRSS and US-measured skin thickness. Several further mechanical instruments exist including the elastometer, twistometer, cutometer and plicometer. They seem to distinguish between involved and non-involved skin, and therefore merit further evaluation. The measurement of late-stage, irreversible skin damage/atrophy should be resolved in the future through the development and validation of new instruments.

OBJECTIVES: To evaluate the construct validity of the European Scleroderma Study Group (EScSG) activity index and to propose modifications if necessary. METHODS: One hundred and thirty-one consecutive patients were investigated and re-evaluated 1 year later. Modified Rodnan skin score (MRSS), skin ulcers and joint contracture numbers, hand anatomic index (HAI), BMI, spirometry, carbon monoxide diffusing capacity (DL(CO)), left ventricular ejection fraction, pulmonary arterial hypertension, HAQ Disability Index (HAQ-DI), patient skin self-assessment questionnaire and several biomarkers were recorded, in addition to the data required for the EScSG activity index. Statistical analysis was performed by categorical principal component analysis (CATPCA). RESULTS: The EScSG activity index appeared in the same dimension as the HAQ-DI, ulcer score and joint contractures, MRSS, patient-reported skin score and HAI by CATPCA. Parameters of lung involvement appeared in another dimension. We constructed a 12-point activity index that was equally associated with both dimensions, by adding the forced vital capacity/DL(CO), change in DL(CO), change in the ulcer scores, HAQ-DI and patient-reported skin score. Biomarkers including vascular endothelial growth factor, soluble P-selectin glycoprotein ligand-1, CRP and albumin were related to both the EScSG and the 12-point index, though they did not improve the total variance of the model. CONCLUSION: The construct validity of the EScSG activity index is good, though the lung-related disease activity may not be sufficiently represented. Further validation steps may be required for both the EScSG and our 12-point activity index.