The number needed to biopsy for cutaneous melanoma in academic dermatology clinics

Abstract

A standard metric for melanoma detection is the number needed to biopsy (NNB). This metric has been used to evaluate practicing dermatologists, dermatology advanced practice professionals, and primary care providers. This metric, however, has rarely been applied to residency clinics. We aimed to determine the NNB at the University of Colorado residency clinics. Moreover, we sought to determine the impact of the coronavirus disease 2019 (COVID-19) pandemic on NNB. This study is a retrospective analysis of biopsies performed from 2016 to 2022 at the Denver Health Medical Center and the Rocky Mountain Regional Veteran Affairs dermatology clinics. Differential diagnosis at the time of biopsy was searched for keywords including melanoma, melanoma in situ, and lentigo maligna. Skin biopsies that included re-excisions were excluded. The NNB was subsequently generated by dividing the number of biopsied lesions with suspected melanoma by the number of histologically confirmed melanomas. The data was further separated by pre-COVID-19 (2016–February 2020), COVID-19 shutdown period (March 2020–July 2020), and post-COVID-19 (March 2020–present). Demographic data, including age, sex, race, and Fitzpatrick type, were collected. There were 2230 biopsies with suspected melanoma in the differential diagnosis at both clinic sites from 2016 to 2022. Of these, 362 were histologically confirmed melanoma. Total NNB was 6.16. The pre-COVID-19 NNB was 5.86, and the post-COVID-19 NNB was 6.91. Residency clinics have NNB similar to published values of practicing dermatologists. Furthermore, within these clinics, the impact of the COVID-19 pandemic was appreciated by a relative, although statistically insignificant, increase in NNB.