Transparency imaging: A new complementary tool for the assessment of melanocytic nevi

Abstract

Transparency imaging: A new Transparency imaging: A new complementary tool for the complementary tool for the assessment of melanocytic nevi assessment of melanocytic nevi Sir, Manual measurement of melanocytic nevi is only performed with rulers which are not satisfactory for irregular and large lesions and give no information about shape. Transparency tracing is a standard measurement tool for skin wound areas, which is reliable, sensitive to changes in size and suitable for routine clinical wound assessment, in most clinical settings. [1][2][3][4] Transparency tracing of skin wounds entails tracing the contour on a transparent film with a permanent pen in order to make periodic comparisons for evaluating treatment outcome by means of overlap of transparency tracing with the real wound contour or by morphometry.In spite of the large experience in wounds, transparency tracing has not yet been applied for the assessment of melanocytic nevi. Transparency tracing could be especially relevant for the assessment of melanocytic nevi in settings with limited access to digital equipment and for measuring intermediate congenital melanocytic nevi. Because the accuracy of baseline images is crucial, our pilot study was focused on this step.The procedure of transparency tracing of melanocytic nevi is explained in Figures 1 and 2. The reproducibility of melanocytic nevi transparency tracing was evaluated by means of scoring the overlap with the real melanocytic nevi contour on 100 common melanocytic nevi lesions from 42 patients (20 males and 22 females). The scoring was performed first over single and later over duplicated transparency tracing by a single observer, as follows:• Single transparency tracing. It was scored as accurate (complete overlap with the outline of the melanocytic nevi lesion) or as inaccurate (incomplete overlap with the melanocytic nevi) • Duplicated transparency tracing (performed twice on the same day). They were scored as accurate (complete overlap both between both transparency tracing and with the real lesion) or as inaccurate (incomplete overlap between them). The reproducibility of the scoring method was evaluated by means of a test-retest, on two separate days (interval of 3-4 weeks, in order to eliminate real changes in melanocytic nevi lesions), and was indirectly tested by means of Cohen's Kappa statistics.In the first set, the strength of agreement of the accuracy scoring single transparency tracing (overlap with the real lesion) was good: Kappa value 0.70; 43 (86%) agreements (SE of Kappa, 0.12; 95% confidence interval from 0.32 to 0.80). In the second set (duplicated transparency imaging), the strength of agreement of transparency imaging accuracy scoring (overlap with the real lesion and with the paired transparency imaging) was "very good": Kappa 0.82; 46 (92%) agreements (SE of Kappa 0.08; 95% confidence interval from 0.66 to 0.98).Our study showed that several factors are important in order to standardize the tracing of transparency tracing: (i) fixing the patient's position, which in...