Accuracy of Skin Cancer Diagnosis Varies by Physician, Exam Method

The accuracy of skin cancer diagnosis varied by lesion type, physician specialty and experience, and examination method, with the greatest accuracy observed for dermatologists using dermoscopy, according to findings from a systematic review and meta-analysis.

Across 100 studies, experienced dermatologists had 5.7-fold higher odds of accurate diagnosis of melanoma using dermoscopy compared with clinical examination, and 13.3-fold higher odds of accurate diagnosis of melanoma using dermoscopic images compared with primary care physicians, reported Maria L. Wei, MD, PhD, of the University of California San Francisco, and colleagues.

Experienced dermatologists also had 2.5-fold higher odds of accurate diagnosis of keratinocytic carcinomas using in-person dermoscopy and dermoscopic images compared with in-person clinical examination and images, they noted in JAMA Dermatology.

Using clinical examination and images, the sensitivity and specificity for diagnosing melanoma were 76.9% and 89.1% for experienced dermatologists, 78.3% and 66.2% for inexperienced dermatologists, and 37.5% and 84.6% for primary care physicians, respectively. When using dermoscopy and dermoscopic images, sensitivity and specificity were 85.7% and 81.3%, 78% and 69.5%, and 49.5% and 91.3%, respectively, for the three groups.

For diagnosing keratinocytic carcinomas, the sensitivity and specificity with experienced dermatologists using clinical examination and clinical images were 79% and 89.1%, respectively, and 83.7% and 87.4% with dermoscopy and dermoscopic images. For primary care physicians using dermoscopy, the sensitivity and specificity were 81.4% and 80.1%.

“We found significant differences in diagnostic accuracy by different physician specialty; accuracy improved when dermoscopic methods were used, and improved further with in-person dermoscopy. These results suggest that clinical examination combined with dermoscopy likely yields better accuracy than either method alone,” wrote Wei and colleagues.

Using the naked eye is the current standard of care for skin cancer examination, and histopathologic testing remains the gold standard for skin cancer diagnosis, the authors explained. As a non-invasive in vivo magnification method, “adding dermoscopy to conventional naked-eye clinical examination in melanoma screening has been associated with more than 40% fewer biopsy procedures performed by dermatologists.”

“Developing technologies could assist in augmenting primary care physicians’ diagnostic performance, increase effectiveness of examination, and increase equitable access to high-quality skin examinations,” they noted. “Furthermore, as suggested by the workplace screening study … and expert consensus panels, a risk-stratified targeted skin-screening approach by dermatologists may be an effective means of detecting skin cancer at a level sufficient to affect outcomes.”

Marcus Butler, MD, of the Princess Margaret Cancer Centre in Toronto, told MedPage Today that “given the increasing incidence of skin cancers in the aging population in North America and elsewhere, this study provides benchmarks for efforts to improve the diagnosis of skin cancers.”

“Such efforts should include specialized dermatological training of primary care providers with dermoscopy, increasing access to experienced dermatologists, and further investigations of novel technologies such as artificial intelligence to augment the high standard of examination by an experienced dermatologist with dermoscopy,” he said.

For this systematic review and meta-analysis, Wei and colleagues searched PubMed, Embase, and Web of Science and included 100 cross-sectional and case-control studies, randomized clinical trials, and nonrandomized controlled trials that used dermatologists or primary care physicians to examine keratinocytic and/or melanocytic skin lesions.

No studies directly comparing dermatologists with primary care physicians using clinical examination/images met eligibility criteria.

Wei and team acknowledged limitations to their study, including the low numbers of physicians in some studies, a lack of data on participants’ race and ethnicity, and regional variations in the use of dermoscopy, which is familiar to at least 50% of primary care physicians in Australia compared with less than 10% in the U.S.

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