Simple counting of nailfold capillary density in suspected systemic sclerosis - 9 years' experience

Capillary damage is a characteristic feature of systemic sclerosis (SSc). This work aimed to explore the potential clinical value of simple microscopic counting of capillary density.

In 325 patients admitted because of a clinical suspicion of SSc and in 80 healthy controls, nailfold capillary microscopy (NCM) was performed using a stereo-zoom microscope in 20 x magnification and with a transparent ruler in one of the eyepieces. Capillaries were counted within 3 mm in the centre of the nailfold in eight fingers.

Capillary density (loops/mm) was decreased in patients with diffuse cutaneous SSc [median 4.7 (range 2.2-7.3)], limited cutaneous SSc [4.9 (2.0-7.3)], earlySSc [4.7 (2.8-7.3)], and preSSc [5.9 (4.3-8.2)] compared to healthy controls [7.2 (5.8-9.0)]. Patients with morphea and with primary Raynaud's phenomenon had normal numbers of capillaries [7.0 (6.2-7.2) and 7.0 (5.3-8.7), respectively]. In only 21/325 (6%) patients was it not possible to count the capillaries because of insufficient transparency of the skin. There was no discrepancy in capillary density based on counts of two or eight fingers. When 43 patients were reassessed after 1 to 4 years, there was no difference between the two assessments.

Determination of capillary density by direct microscopy counts, a simple, inexpensive and rapid method, helps to identify patients with SSc, early in the disease course and in patients with very limited skin involvement.