Accuracy of Skin Cancer Diagnosis by Physician Assistants Compared With Dermatologists in a Large Health Care System

Importance: Physician assistants (PAs) are increasingly used in dermatology practices to diagnose skin cancers, although, to date, their diagnostic accuracy compared with board-certified dermatologists has not been well studied. Objective: To compare diagnostic accuracy for skin cancer of PAs with that of dermatologists. Design, Setting, and Participants: Medical record review of 33 647 skin cancer screening examinations in 20 270 unique patients who underwent screening at University of Pittsburgh Medical Center-affiliated dermatology offices from January 1, 2011, to December 31, 2015. International Classification of Diseases, Ninth Revision code V76.43 and International Classification of Diseases and Related Health Problems, Tenth Revision code Z12.83 were used to identify pathology reports from skin cancer screening examinations by dermatologists and PAs. Exposure: Examination performed by a PA or dermatologist. Main Outcomes and Measures: Number needed to biopsy (NNB) to diagnose skin cancer (nonmelanoma, invasive melanoma, or in situ melanoma). Results: Of 20 270 unique patients, 12 722 (62.8%) were female, mean (SD) age at the first visit was 52.7 (17.4) years, and 19 515 patients (96.3%) self-reported their race/ethnicity as non-Hispanic white. To diagnose 1 case of skin cancer, the NNB was 3.9 for PAs and 3.3 for dermatologists (P < .001). Per diagnosed melanoma, the NNB was 39.4 for PAs and 25.4 for dermatologists (P = .007). Patients screened by a PA were significantly less likely than those screened by a dermatologist to be diagnosed with melanoma in situ (1.1% vs 1.8% of visits, P = .02), but differences were not significant for invasive melanoma (0.7% vs 0.8% of visits, P = .83) or nonmelanoma skin cancer (6.1% vs 6.1% of visits, P = .98). Conclusions and Relevance: Compared with dermatologists, PAs performed more skin biopsies per case of skin cancer diagnosed and diagnosed fewer melanomas in situ, suggesting that the diagnostic accuracy of PAs may be lower than that of dermatologists. Although the availability of PAs may help increase access to care and reduce waiting times for appointments, these findings have important implications for the training, appropriate scope of practice, and supervision of PAs and other nonphysician practitioners in dermatology.