Reliability and inter-observer agreement of dermoscopic diagnosis of melanoma and melanocytic naevi

The aim of this study was to analyse the reliability and the inter-observer agreement of dermoscopy in the diagnosis of melanocytic skin lesions. Nine dermatologists, with a different training experience and who routinely use d dermoscopy in different hospitals in Italy, evaluated clinical and dermos copy photographs of 15 melanocytic lesions (four invasive melanomas, four h istologically common naevi, and seven naevi with histological atypia), A fu rther series of dermoscopic photographs of 40 melanocytic lesions was evalu ated to quantify inter-observer concordance in recognizing dermoscopic crit eria. Compared to the true (histological) diagnosis, clinical diagnosis (ca tegories: melanoma, common naevus, atypical naevus) was correct in 40% of c ases (range, 27-53%), The percentage raised to 55% (40-73%) by the use of d ermoscopy, with an average improvement of 15.6%, Concerning melanoma, clini cal diagnosis resulted in a sensitivity of 41.9%, specificity of 77.8%, pos itive predictive value (PPV) of 36.1%, negative predictive value (NPV) of 8 1.8%, By using dermoscopy, an improvement of diagnostic performance was fou nd (sensitivity 75%, specificity 88.8%, VPP 71.0%, VPN 90.7%), The inter-ob server agreement in melanoma diagnosis, by using dermoscopy, was similar to that obtained by clinical examination (k statistics = 0.54 and 0.52, respe ctively). Concerning dermoscopic criteria, the best agreement among observe rs was found for pseudopods, a dermoscopic parameter related to the radial growth phase of melanoma, We conclude that dermoscopy is an useful tool for a non-invasive diagnosis of melanocytic skin lesions, improving the diagno stic performance compared to clinical examination. (C) 1998 Lippincott Will iams & Wilkins.