Diagnostic Accuracy of Smartphone-Based Patient-Initiated Store-and-Forward Teledermatology: A Cross-Sectional Direct-to-Specialist Study

Background: Smartphone-based store-and-forward teledermatology (SAF-TD) has emerged as a potential approach to improving access to dermatological care. Patient-initiated SAF-TD systems, which enable direct image submission to dermatology specialists, represent an increasingly relevant but insufficiently studied model. However, diagnostic agreement remains insufficiently characterized in real-world, patient-initiated, direct-to-specialist systems in which adult patients independently submit conventional smartphone photographs and assessments are performed by dermatologists with different levels of clinical experience. Methods: A prospective cross-sectional, single-center study was conducted between February 2022 and September 2024, which included 83 patients. Patients independently submitted conventional smartphone photographs through a hospital patient portal. Diagnoses established remotely by an experienced and a beginner dermatologist were compared with face-to-face (FTF) diagnoses as the reference standard. Melanocytic lesions were defined as the positive category and non-melanocytic conditions as the negative category. Diagnostic agreement was assessed using Cohen’s kappa, and sensitivity and specificity were calculated with 95% confidence intervals (CIs). Results: Agreement between SAF-TD and FTF classification was 91.6% (95% CI, 83.6–95.9) for the experienced dermatologist (κ = 0.781; 95% CI, 0.628–0.934) and 90.4% (95% CI, 82.1–95.0) for the beginner dermatologist (κ = 0.760; 95% CI, 0.603–0.917), indicating substantial agreement. Sensitivity and specificity were 94.7% (95% CI, 75.4–99.1) and 90.6% (95% CI, 81.0–95.6), respectively, for the experienced dermatologist and 86.4% (95% CI, 66.7–95.3) and 91.8% (95% CI, 82.2–96.4), respectively, for the beginner dermatologist. Conclusions: Patient-initiated smartphone-based SAF-TD demonstrated substantial agreement with FTF binary classification by both dermatologists. These findings support its potential clinical use as a complementary method for initial remote dermatological assessment. However, the results require validation in larger, multicenter studies.