Use of morphologic characteristics in dermoscopic diagnosis

August 12, 2016

Abstract

Importance   
Both colors and structures are considered important in the dermoscopic evaluation of skin lesions but their relative significance is unknown.

Objective  
To determine if diagnostic accuracy for common skin lesions differs between gray-scale and color dermoscopic images.

Design, Setting, and Participants  
A convenience sample of 40 skin lesions (8 nevi, 8 seborrheic keratoses, 7 basal cell carcinomas, 7 melanomas, 4 hemangiomas, 4 dermatofibromas, 2 squamous cell carcinomas [SCCs]) was selected and shown to attendees of a dermoscopy course (2014 Memorial Sloan Kettering Cancer Center dermoscopy course). Twenty lesions were shown only once, either in gray-scale (n = 10) or color (n = 10) (nonpaired). Twenty lesions were shown twice, once in gray-scale (n = 20) and once in color (n = 20) (paired). Participants provided their diagnosis and confidence level for each of the 60 images. Of the 261 attendees, 158 participated (60.5%) in the study. Most were attending physicians (n = 76 [48.1%]). Most participants were practicing or training in dermatology (n = 144 [91.1%]). The median (interquartile range) experience evaluating skin lesions and using dermoscopy of participants was 6 (13.5) and 2 (4.0) years, respectively.

Main Outcomes and Measures  
Diagnostic accuracy and confidence level of participants evaluating gray-scale and color images. Two separate analyses were performed: (1) an unpaired evaluation comparing gray-scale and color images shown either once or for the first time, and (2) a paired evaluation comparing pairs of gray-scale and color images of the same lesion.

Results  

In univariate analysis of unpaired images, color images were less likely to be diagnosed correctly compared with gray-scale images (odds ratio [OR], 0.8; P<.001).  Using gray-scale images as the reference, multivariate analyses of both unpaired and paired images found no association between correct lesion diagnosis and use of color images (OR, 1.0; P=.99, and OR, 1.2 P=.82, respectively). Stratified analysis of paired images using a color by diagnosis interaction term showed that participants were more likely to make a correct diagnosis of SCC and hemangioma in color (P < .001 for both comparisons) and dermatofibroma in gray-scale (P< .001).

Conclusions and Relevance  

Morphologic characteristics (ie, structures and patterns), not color, provide the primary diagnostic clue in dermoscopy. Use of gray-scale images may improve teaching of dermoscopy to novices by emphasizing the evaluation of morphology.

Source:

Bajaj, S, et al.  The Role of Color and Morphologic Characteristics in Dermoscopic Diagnosis JAMA Dermatol. 2016;152(6):676-682. doi:10.1001/jamadermatol.2016.0270.  http://archderm.jamanetwork.com/article.aspx?articleid=2502286

See also:

I was pleased to note the results supported my opinion that dermatoscopic diagnosis of skin lesions can be as accurate, or perhaps more accurate, using grey-scale/black-and-white images compared to colour images.  I am currently planning a similar study with our own data.

Source: Dermatology Research Review, Issue 22 – 2016.  Comment from Associate Professor Amanda Oakley, a specialist dermatologist in Hamilton and an Honorary Associate Professor at Waikato Clinical School, University of Auckland School of Medicine.
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