COMPUTER-BASED QUANTITATIVE-ANALYSIS OF CAPILLARY ABNORMALITIES IN SYSTEMIC-SCLEROSIS AND ITS RELATION TO PLASMA-CONCENTRATION OF VON-WILLEBRAND-FACTOR

Objectives-To evaluate an objective and quantitative method for assess ment of capillary abnormalities in systemic sclerosis (SSc). Methods-N ailfold capillaries were investigated by capillary microscopy and phot ographed in 17 consecutive SSc patients (five with diffuse cutaneous s ystemic (dSSc) and 12 with limited systemic sclerosis (1SSc)) and in 1 7 healthy controls. Investigators having no access to clinical data ma de drawings from magnified projections of coded photographs and analys ed them using a computer program. Capillary density (capillary loops/m m in the distal row) and median capillary loop area were calculated. P resence of functional or organic arterial changes was evaluated by mea surement of finger pressure with finger cooling. Plasma concentration of von Willebrand factor (VWF) was analysed using an enzyme linked imm unosorbent assay (ELISA). Results-In 16 of 17 SSc patients and 13 of 1 7 controls the technical quality of the photographs was sufficient for computer analysis. Capillary density was decreased in dSSc (median 6. 9 loops/mm) and in dSSc (median 3.8 loops/mm) compared with healthy co ntrols (8.9 loops/mm) and median capillary loop area was increased in dSSc (7.3 x 10(-3) mm(2)) and in ISSc (8.5 x 10(-3) mm(2)) compared wi th healthy (5.0 x 10(-3) mm(2)). An inverse was found between capillar y density and median capillary loop area in SSc patients. Plasma VWF w as increased in patients (median 401 IE/l in dSSc and 409 IE/l in ISSc ) compared with controls matched for age and sex (median 276 IE/l). Co mputer based analysis showed capillary density below the control range and median capillary loop area above the control range in 14 of 16 SS c patients. Measurement of finger pressure with finger cooling showed organic vascular changes in nine of 13 SSc patients.Conclusion-Compute r based quantitative analysis has low interobserver variability and is a quantitative and sensitive method of assessing capillary abnormalit ies in SSc.