Objective. To test the intra-and interobserver variability, among clinicians with an interest in systemic sclerosis (SSc), in defining digital ulcers.Methods. Thirty-five images of finger lesions, incorporating a wide range of abnormalities at different sites, were duplicated, yielding a data set of 70 images. Physicians with an interest in SSc were invited to take part in the Web-based study, which involved looking through the images in a random sequence. The sequence differed for individual participants and prevented crosschecking with previous images. Participants were asked to grade each image as depicting "ulcer" or "no ulcer," and if "ulcer," then either "inactive" or "active." Images of a range of exemplar lesions were available for reference purposes while participants viewed the test images. Intrarater reliability was assessed using a weighted kappa coefficient with quadratic weights. Interrater reliability was estimated using a multirater weighted kappa coefficient.Results.
Conclusion.The poor interrater reliability suggests that if digital ulceration is to be used as an end point in multicenter clinical trials of SSc, then strict definitions must be developed. The present investigation also demonstrates the feasibility of Web-based studies, for which large numbers of participants can be recruited over a short time frame.Digital ulcers, which are common in patients with systemic sclerosis (SSc) (1,2), are painful and disabling. These types of ulcers are often used as a primary end point in clinical trials of SSc-related digital ischemia and vasculopathy, as was the case in 2 recent multicenter placebo-controlled trials (3,4). Patient-assessed digital ulcer "activity" was among a core set of measures proposed for use in trials of SSc-related Raynaud's phenomenon (5). However, digital ulcers are difficult to define, which raises concerns about their reliability as an outcome measure. Problems include 1) making the distinction between "healed" and "nonhealed" ulcers, which can be difficult with lesions situated on the fingertips and the extensor surfaces, since an ulcer crater can persist for months after an acute episode, and 2) determining which sites to use. The study by Korn et al (3) included only those ulcers at or distal to the proximal interphalangeal joints, and yet, more proximal ulcers (e.g., those over the metacarpophalangeal joints) can be very painful, and healing can be difficult.