NIHR Signal Dermoscopy plus visual inspection aids melanoma diagnosis
Published on 5 March 2019
Dermoscopy, using a relatively cheap handheld magnifying device alongside naked eye observation, is more accurate in the diagnosis of melanoma than visual inspection alone. It can also provide a photographic record which can be used for reference during follow-up.
This NIHR-funded review included 104 studies of skin lesions in the dermatology clinic that looked suspicious or were present in those at high risk of developing melanoma. Melanoma is a rare form of skin cancer. Inspection of the lesions in-person using dermoscopy was also more accurate than looking at dermoscopic images remotely.
The findings provide stronger evidence to support current guidelines for the use of dermoscopy in the assessment of suspicious pigmented skin lesions in secondary care and support further training of non-specialists in the technique.
- Cancers, Diagnostics, Skin conditions, Primary care, Acute and general medicine
Why was this study needed?
Melanoma was the fifth most common cancer in the UK in 2015, with 15,900 new cases each year. Over the last decade, incidence rates have increased by 50%.
Without treatment, melanoma can spread to other parts of the body. Visual inspection is usually one of the first steps taken in the diagnosis of a suspicious looking skin lesion. However, magnification techniques such as dermoscopy are increasingly being used by GP’s and specialists to assess whether high-risk lesions, because of appearance or family history, could be cancerous. The method uses magnification and a strong light provided in a small handheld device to allow physicians to examine the fine patterns in the top layers of skin in more detail, through an oil interface.
This Cochrane review aimed to investigate the accuracy of dermoscopy compared to visual inspection and whether there was a difference if skin specialists used the device themselves compared with looking at clinical images that had been sent to them.
What did this study do?
This systematic review included 104 studies (42,788 skin lesions) that evaluated the use of dermoscopy in adults with suspicious skin lesions either in-person or remotely.
The studies included pigmented skin lesions, atypical moles, lesions suspicious of melanoma or lesions in those who were at high risk of developing melanoma based on information such as family history. Most studies were European, with three studies from the UK.
Inclusion of a wide range of study types, selective recruitment of participants and inconsistency in the reporting of study conduct does impact the reliability of the results.
As the average prevalence of melanoma was 12% in the in-person studies and 25% in the remote studies, this suggests a specialist population such as those attending dermatology outpatients and with higher likelihood of melanoma than is seen by GPs.
What did it find?
- Meta-analyses of data from 26 in-person studies comparing dermoscopy plus visual inspection to 13 in-person visual inspection studies suggested that using dermoscopy was over four times more accurate than visual inspection on its own.
- Similar results were found when comparing 60 image-based dermoscopy studies to 11 image-based visual inspection studies. Dermoscopic images were five times more accurate.
- Interpreting these results for a hypothetical group of 1,000 patients with a 12% chance of having a melanoma, suggests that 110 correct diagnoses (true positives) could be made in the dermoscopy group and 91 in the visual inspection only group - if a 20% unnecessary excisions (false positive) rate is accepted.
- In the same group of 1,000 hypothetical patients, 44 unnecessary excisions (false positives) might occur in the dermoscopy group and 220 in the visual inspection group if a 20% missed diagnosis (false negative) rate is accepted.
- Overall, accuracy was found to be higher for in-person diagnoses using dermoscopy compared with image-based dermoscopy evaluations.
- The review also found that accuracy of interpretation was increased when the diagnosis of melanoma was made by individuals with more expertise and training.
What does current guidance say on this issue?
The NICE 2017 Clinical Knowledge Summary supports the use of dermoscopy for assessment of lesions in primary care, prior to referral for potential biopsy or removal of the lesion. The NICE 2015 guideline also recommends using dermoscopy in the assessment of all pigmented skin lesions that have been either referred for assessment or identified during follow-up in secondary or tertiary care.
The NICE guideline further advises the use of dermoscopy to take photographic images at first presentation of an atypical skin lesion. The images should then be used as a comparison when reviewing the clinical appearance of the lesion three months later to identify potential early signs of melanoma.
What are the implications?
The review mostly looked at the use of dermoscopy by dermatologists in secondary care where it is in standard use in the NHS. This review supports that practice.
However, GPs with specialist interests in dermatology are increasingly using dermoscopy, often sending images to secondary care for review. Few studies in this review looked at this application for triaging who needs to be seen in person.
However, depending on the level of training, this study suggests that accuracy is improved by in-person assessment.
Citation and Funding
Dinnes J, Deeks JJ, Chuchu N et al; Cochrane Skin Cancer Diagnostic Test Accuracy Group. Dermoscopy, with and without visual inspection, for diagnosing melanoma in adults. Cochrane Database Syst Rev. 2018;12:CD011902.
This project was funded by the National Institute for Health Research (NIHR) Cochrane Systematic Reviews Programme Grant (13/89/15).
Cancer Research UK. Melanoma skin cancer statistics. London: Cancer Research UK; 2015.
NHS website. Skin cancer (melanoma). London: Department of Health and Social Care; 2017.
NICE. Melanoma and pigmented lesions. Clinical Knowledge Summary. London: National Institute for Health and Care Excellence; 2017.
NICE. Melanoma: assessment and management. NG14, London: National Institute for Health and Care Excellence; 2015.
In this analysis, the bottom line is that when used in the clinic by dermatologists, per 1,000 lesions assessed, the number of missed melanomas is reduced using dermoscopy. One hundred and ten melanomas would be correctly identified compared with 91 on visual inspection alone. The number of unnecessary excisions would also be reduced. It was calculated that 220 incorrect melanoma excisions would be made versus 44 lesions in the dermoscopy group.
This means dermatologists should be using dermoscopy to assess pigmented lesions and is in line with NICE guidance. The report makes some comments about algorithms (most useful for training practitioners) and use in primary care (little evidence) which suggests some evidence gaps.
Dr Michael Ardern-Jones, Associate Professor and Consultant Dermatologist, University of Southampton
The commentator declares no conflicting interests
This review looks at a large number of studies of dermoscopy. The authors demonstrate a consistent and significant pattern, indicating that use of dermoscopy increases the likelihood of diagnosing melanoma more accurately, with reduction in unnecessary surgery.
Dermoscopy is now practiced widely by dermatologists, and this detailed, thorough review strongly supports the continued use of dermoscopy in the diagnosis of melanoma.
Moreover, many who presently use dermoscopy are not yet experts and should be encouraged to deepen their skills. Non-dermatologists should be encouraged to take on dermoscopy, and medical schools should consider teaching dermoscopy as part of core curriculum.
Professor Colin Fleming, Consultant Dermatologist, Honorary Professor of Dermatology, Ninewells Hospital and Medical School
The commentator declares no conflicting interests