ab17_2

Capillary density in patients with systemic sclerosis, as determined by microscopy counts and compared with computer-based analysis

M. Wildt, R. Hesselstrand, A. Scheja, A. Åkesson

Department of Rheumatology, Lund University Hospital, Lund, Sweden

ABSTRACT
Objective
To develop a method enabling capillary density to be determined rapidly and accurately in patients with systemic sclerosis.

Method
Capillary density was determined in 11 controls and 22 patients: 5 with diffuse cutaneous systemic sclerosis (dSSc), 12 with limited cutaneous systemic sclerosis (lSSc), 2 with suspected systemic sclerosis (suspSSc), 2 with sclerodermatomyositis, and 1 with undifferentiated connective tissue disease. Using a microscope equipped with a graticule, nailfold capillaries were counted within a 3 mm length of the nailfold; these counts were made by 4 different observers. The results were compared with the corresponding values obtained by the computer-based analysis of photographs.

Results
The median capillary density according to the direct counts was 8.0 loops/mm (6.7 - 10.0) in the controls, 6.0 loops/mm (range 4.8 - 8.8) in the dSSc subgroup, 5.6 loops/mm (4.2 - 6.5) in the lSSc subgroup, and 7.2 loops/mm (6.2 - 8.2) in the suspSSc subgroup. In the series as a whole, there was no significant difference between the median values for the left hands and those for the right hands, nor between the median value for all digit IVs and the median value for all four digits analysed (II, III, IV, and V). Inter-observer variation was small between the 4 different observers. Direct microscopy counts were slightly higher than the corresponding values obtained by computer-based analysis.

Conclusion
Direct microscopy counting is a rapid, simple, and reliable means of determining capillary density for screening purposes.

Key words
Systemic sclerosis, capillary density, capillary microscopy.

The study was supported by grants from the Osterlund Foundation, the Kock Foundation, the Medical Faculty of the University of Lund, and the Medical Research Council (project no. 11628).

Please address correspondence and reprint requests to: Dr. Agneta Scheja, Department of Rheumatology, Lund University Hospital, S-221 85 Lund, Sweden.