BT19 Teledermatology preserves the number needed to biopsy for diagnosis of skin cancer

Abstract

Abstract In order to ensure a high sensitivity and prevent a missed skin cancer diagnosis, specificity is sacrificed. The number needed to biopsy (NNB) describes the number of benign lesions excised in order to diagnose one skin cancer. Published NNBs are highly variable, but a 2020 meta-analysis reported the overall NNB for melanoma to be 9.6 (Petty AJ, Ackerson B, Garza R et al. Meta-analysis of number needed to treat for diagnosis of melanoma by clinical setting. J Am Acad Dermatol 2020; 82:1158–65). The overall NNB is reported to be 3 for any skin cancer and 1.6 for nonmelanoma skin cancer (Matsumoto M, Secrest A, Anderson A et al. Estimating the cost of skin cancer detection by dermatology providers in a large health care system. J Am Acad Dermatol 2018; 78:701–9). The incidence of skin cancer is rising significantly in the UK, placing increased pressures on dermatology departments. A growing body of evidence suggests that the diagnostic accuracy of teledermatology is similar to that of face-to-face (F2F) care and many trusts now employ teledermatology for triage of 2-week wait (2WW) referrals. Our trust uses a teledermatology model where all patients referred via the 2WW pathway complete a digital form with details of the lesion. Both clinical and dermoscopic images are taken by a trained medical photographer and reviewed by a consultant dermatologist. Lesions felt to be suspicious for malignancy are triaged directly for biopsy. We aimed to evaluate the effectiveness of our teledermatology service by calculating the NNB, as well as the number of appointments where a biopsy was not performed following F2F assessment. Over a 2-month period, 251 lesions in 221 patients were triaged for biopsy via teledermatology, and 212 were biopsied following a F2F assessment. Of these, 54 (25.5%) were histologically diagnosed as skin cancer [11 melanoma, nine squamous cell carcinoma (SCC) and 33 basal cell carcinoma (BCC)]. When comparing the teledermatology diagnosis with the histological diagnosis, the overall NNB for skin cancer was 3.9. The NNB varied depending on the type of lesion suspected (7 for melanoma, 7.1 for SCC and 1.6 for BCC). When examining our NNB, it seems the accuracy of our teledermatology service is in keeping with data published from other centres. Furthermore, only a small proportion of lesions (10%) were not biopsied following a F2F assessment, demonstrating that teledermatology probably has a similar accuracy to F2F assessment. Although this is a small study from one centre, it further demonstrates that teledermatology is an efficient use of resources with no clear reduction in diagnostic accuracy.