BACKGROUND:Recurrent aphthous stomatitis (RAS) is characterized by painful recurrent oral ulcers and is typically diagnosed via history and clinical examination. Our aim was to validate a set of anamnestic diagnostic criteria (RASDX) to increase the accuracy of RAS diagnosis, particularly when a clinical examination is not feasible. METHODS:Participants were enrolled during an unmatched case-control study. RASDX consisted of an initial phone screening using standardized questionnaires and recognition of RAS photographs in the clinic. The proportion of agreement with an examination by an oral medicine expert was calculated. RESULTS:A total of 115 participants were scheduled for a clinical diagnostic visit and 11 were withdrawn. The remaining 104 participants were aged 18-50 years, 54% women, 64% White and 20% Hispanic. Of these, all 49 controls with negative RASDX had no clinical ulcers. Of the 54 cases diagnosed with RAS by RASDX, 53 were clinically confirmed to have RAS lesions (99% agreement; exact one-sided 95% CI = 95-100%). CONCLUSIONS:RASDX, based on a combination of history and photograph recognition, was highly accurate compared with a diagnosis that employed an oral examination.