Diagnostic accuracy of dermoscopy - Dermatology

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dermoscopy was significantly higher than that achieved without dermoscopy (4.0 [95% CI 3.0 to 5.1] versus 2.7 [1.9 to 3.4]), resulting in a mean difference of 1.3 (0.7 to 2.0), or an improvement of 49% (p = 0.001). The second model included the results of all 27 eligible studies and yielded similar results. The mean log odds ratio achieved with dermoscopy was again significantly higher than that achieved without dermoscopy (3.4 [2.9 to 3.9] versus 2.5 [1.9 to 3.1], p = 0.03). Inclusion of information on the experience of the examiners showed that the diagnostic performance of dermoscopy was significantly better for experts than for non-experts (mean log odds ratio 3.8 [3.3 to 4.3] versus 2.0 [1.4 to 2.6]; mean difference 1.8 [0.8 to 2.7], p = 0.001). To account for this finding, we generated a model that compared the performance of the clinical diagnosis without dermoscopy, dermoscopy by non-experts, and dermoscopy by experts. For each of the methods, SROC curves were constructed (Figure 2). The clinical diagnosis without dermoscopy showed similar diagnostic accuracy to dermoscopy by non-experts (mean log odds ratio 2.5 versus 2.0; mean difference 0.5 [95% CI for difference -0.4 to 1.4], p = 0.65). For both approaches the diagnostic accuracy was significantly lower than that achieved with dermoscopy by experts (mean log odds ratio 3.8, p = 0.003 and p = 0.001). The influence of study characteristics on the diagnostic performance of dermoscopy was investigated by univariate and multivariate regression analysis including the results of all eligible studies. As in the analysis above, the diagnostic performance of dermoscopy increased for experts (regression coefficient 1.8 [95% CI 0.8 to 2.8], p < 0.001). The diagnostic performance also increased when the Sensitivity 162 Review 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 Without dermoscopy Dermoscopy when performed by experts Dermoscopy when performed by non-experts 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1Specificity Figure 2. SROC curves for the performance of the clinical diagnosis without dermoscopy (red line), dermoscopy by experts (black line), and dermoscopy by non-experts (blue line). Dermoscopy diagnosis was made by a group of two or more examiners in consensus (regression coefficient 1.1 [0.2 to 2.1], p = 0.02). Although consensus increased the discriminatory power of dermoscopy, the procedure performed by experts achieved higher accuracy than inspection with the unaided eye whether or not the dermoscopic diagnosis was made in consensus. The accuracy of the (clinically more relevant) non-consensus diagnosis achieved with dermoscopy was significantly higher than that achieved without dermoscopy (mean log odds ratio 3.7 versus 2.5; mean difference 1.2 [95% CI for difference 0.3 to 2.2], p = 0.01). The diagnostic ability of dermoscopy was inversely correlated with the prevalence of melanoma in the sample (regression coefficient -0.04 [95% CI -0.06 to -0.01], p = 0.006) and lower for experimental studies that used presentation of slides, colour prints, or digital images than for clinical studies in which the diagnosis was made face to face (regression coefficient -1.3 [-2.1 to -0.5], p = 0.001). Other study characteristics did not significantly influence the diagnostic performance of dermoscopy. For multivariate analysis we used a forward stepwise regression analysis. The final model included three variables: the experience of examiners (regression coefficient 1.2 [0.3 to 2.1], p = 0.01), the prevalence of melanoma (regression coefficient -0.04 [-0.06 to -0.01], p = 0.01), and whether the diagnosis was made in consensus (regression coefficient 1.0 [0.04 to 1.9], p = 0.04). Other variables were not independently associated with the diagnostic accuracy of dermoscopy. Since the dermatologists’ experience was the strongest predictive variable for the diagnostic performance of dermoscopy, we built a SROC model for the pooled diagnostic performance of dermoscopy adjusted for three settings with different degrees of experience (Figure 3). Univariate analysis of the individual results of all eligible studies showed that the diagnostic accuracy of dermoscopy was similar for the different diagnostic algorithms. The log odds ratios achieved with pattern analysis (3.6 [95% CI 2.8 to 4.4]), the ABCD rule (3.2 [2.4 to 3.9]), and scoring systems (3.1 [2.1 to 4.0]) did not differ significantly (p = 0.64). We analysed the influence of the experience of the examiners on the performance of the diagnostic algorithms. The degree of experience had a significant effect on the diagnostic accuracy of pattern analysis (regression coefficient 2.0 [95% CI 0.4 to 3.6], p = 0.02) and scoring systems (regression coefficient 2.3 [0.5 to 4.1], p = 0.02). By contrast, the degree of experience had no significant effect on the diagnostic accuracy achieved with the ABCD rule (regression coefficient 0.8 [-1.1 to 2.7], p = 0.35). Discussion This meta-analysis of 27 studies provides evidence that dermoscopy gives better diagnostic accuracy for melanoma than clinical inspection without dermatoscopy (ie with the unaided eye). This conclusion accords with that of a previous review, which included six studies, 37 and another meta-analysis, which included eight studies. 38 The review did not provide a quantitative analysis and the other metaanalysis was restricted to studies that directly compared the THE LANCET Oncology Vol 3 March 2002 http://oncology.thelancet.com For personal use. Only reproduce with permission from The Lancet Publishing Group.
Sensitivity Dermoscopy 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Best case Base case Worst case 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1Specificity Figure 3. SROC curves for the pooled diagnostic performance of dermoscopy. The base case (black line) is adjusted to a setting at which half of the examiners are experienced in dermoscopy (experts). The best case (red line) is adjusted to a setting at which all examiners are experts in dermoscopy. The worst case (blue line) is adjusted to a setting at which all examiners are untrained or less experienced (non-experts). diagnostic performance with and without dermoscopy. Neither study addressed the influence of study characteristics on the diagnostic performance of dermoscopy. According to our analysis, the diagnostic accuracy of dermoscopy significantly depends on the experience of the examiners. Moreover, the diagnostic accuracy achieved is no better with dermoscopy applied by non-experts than with the unaided eye. This finding underlines the importance of training for the application of dermoscopy. 5,6 The study by Westerhoff and colleagues, investigating the value of dermoscopy on the diagnostic performance of primary-care physicians, deserves further attention. 36 It was the only study of non-dermatologists. Primary-care physicians were trained to use a simplified diagnostic scoring system for dermoscopy. Their diagnostic performance before training was only slightly better than chance. After training, there was a significant improvement in the diagnosis of melanoma by dermoscopy versus inspection with the unaided eye. However, the reported diagnostic accuracy after training was much lower than in comparable studies involving dermatologists. We also found that the diagnostic performance of dermoscopy was improved when the diagnosis was made by a group of examiners in consensus. A consensus diagnosis might not be practicable in most clinical settings, but it may be important for telemedical applications. By electronic transmission of digital dermoscopic images, teledermoscopy potentially involves two or more experts at Review geographically distant facilities. However, how a consensus can be reached for a group of examiners working at geographically distant facilities is unclear. Two studies that compared face-to-face diagnosis with remote diagnosis found no differences in the diagnostic performances, indicating that electronically transmitted dermoscopic images convey the information necessary for differentiation between melanoma and non-melanoma. 39,40 Future work should assess the value of a consensus diagnosis for electronically transmitted dermoscopic images. The prevalence of melanoma was inversely correlated with the diagnostic accuracy of dermoscopy. A possible interpretation of this finding is that if more melanomas are included in a sample, the overall diagnostic difficulty of the sample is increased. Another explanation could be differences in the criteria applied to select the lesions between the studies. Since the original reports by Pehamberger, Steiner, and colleagues, 3,9,35 describing the use of pattern analysis for the dermoscopic assessment of pigmented skin lesions, several diagnostic algorithms have been developed. Pattern analysis relies on the description of several dermoscopic features, which can be difficult for non-experts to recognise. Scoring systems are simplified versions of pattern analysis with a limited number of dermoscopic features. The ABCD rule is somewhat different from the other algorithms because the exact description of the dermoscopic features is not so important. Pattern analysis requires a sufficient amount of training, 6 whereas the other, simpler, diagnostic algorithms might be more suitable for less experienced examiners. 4,12 In our analysis, all algorithms did equally well. Pattern analysis showed slightly better diagnostic accuracy than the other algorithms but the differences were not statistically significant. As expected, the diagnostic performance of pattern analysis was strongly influenced by the experience of the examiners. Surprisingly, this was also true for scoring systems. One explanation might be that, as for pattern analysis, the recognition of dermoscopic features is crucial for the diagnostic procedure. Compared with pattern analysis and scoring systems, the degree of experience had less influence on the diagnostic ability of the ABCD rule for dermoscopy, which suggests that this algorithm is especially suitable for beginners in dermoscopy. As shown by the SROC curves in Figure 3, the diagnostic accuracy of dermoscopy does not reach 100% even under the assumption of optimum conditions, indicating that dermoscopy cannot replace histopathology. However, dermoscopy may provide useful additional information for the histopathologist in difficult cases. Soyer and colleagues showed that clinicopathological correlation of pigmented skin lesions by dermoscopy is useful for dermatopathologists when reporting on melanocytic skin lesions. 41 Dermoscopy and histopathology should be regarded as concurrent examinations of a joint diagnostic procedure with additive information. The summary estimates of the diagnostic accuracy of dermoscopy provided by this meta-analysis have to be interpreted with caution because the results of most studies were potentially influenced by verification bias, which is likely to occur when the decision to proceed with the THE LANCET Oncology Vol 3 March 2002 http://oncology.thelancet.com 163 For personal use. Only reproduce with permission from The Lancet Publishing Group.
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Diagnostic accuracy of dermoscopy - Dermatology

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