Digital ulcers (DUs) are a major problem in patients with systemic sclerosis (SSc), causing severe pain, and impairment of hand function. In addition, DUs heal slowly and sometimes become infected, which can lead to gangrene and necessitate amputation, without appropriate intervention. A reliable, objective method for assessing DU healing or progression is needed in both clinical and research arenas. The objectives were: (1) to compare two digital planimetry methods of DU area measurement (ellipse and free hand region-of-interest [ROI]) applied to photographs of DUs, and (2) to assess reliability of photographic calibration and the two area measurement methods.
107 DUs from 36 patients with SSc-spectrum disease were photographed. Three raters assessed the photographs. Custom software allowed raters to calibrate photograph dimensions, and draw ellipse/free-hand ROIs. Shapes/dimensions for ROIs were saved for further analysis.
Calibration (single rater, 5 repeats/image) produced an intra-class correlation co-efficient (intra-rater reliability) of 0.99. Mean (SD) areas of DUs assessed using ellipse and free-hand ROIs were 18.7 (20.2) mm2 and 17.6 (19.3) mm2, respectively. Intra- and inter-rater reliability of the ellipse ROI was 0.97 and 0.77, respectively. For the free hand ROI, the intra- and inter-rater reliability was 0.98 and 0.76.
This study shows digital planimetry methods applied to SSc-related DUs can be extremely reliable. Further work is now needed to move towards applying these as outcome measures for clinical trials, and in clinical settings.