Analyzing Differences in Diagnostic Accuracy of a Pigmented Lesion Assay for Melanoma

Background. Standard protocol to detect melanoma relies on visual assessment in which the sensitivity and specificity are low for early melanomas. Pigmented lesion assay (PLA) offers objective metrics to aid in determining suspicious lesions; however, the literature on the diagnostic accuracy is controversial. Methods. To assess the performance of PLA, we retrospectively assessed the diagnostic accuracy using two different cohorts, total (n = 426) and biopsied (n = 96), modifying the definition of true negative for each. Sensitivity, specificity, negative predictive value, positive predictive value, prevalence, and Cohen's kappa were calculated. Results. 370 PLA (-) lesions and 56 in the PLA (+). Of the 40 PLA (-) lesions that were biopsied, 5 (12.5%) were diagnosed as melanoma and 16 (40.0%) were atypical melanocytic nevus. Of the 56 PLA (+) lesions, 14 (25.0%) were melanoma, of which 10 (71.4%) were double positive, 3 (21.4%) were PRAME only, and 1 (7.1%) was LINC only. For the total cohort (n = 426), sensitivity of 73.7%, specificity of 89.7%, NPV of 98.6%, PPV of 25.0%, prevalence of 4.5%, accuracy of 89.0%, and kappa agreement of 0.329 were calculated. The biopsied cohort revealed the same sensitivity and PPV; however, specificity was 45.5%, accuracy was 51.0%, NPV was 87.5%), and kappa agreement was 0.110. Conclusion. There differences in our study seen between cohorts highlight the importance to recognize that neither findings are perfect. The real value likely falls in between, but further studies are needed.