Diagnosing skin cancer in primary care: how do mainstream general practitioners compare with primary care skin cancer clinic doctors?

Abstract

Objective: To measure and compare the casemix and diagnostic accuracy of excised or biopsied skin lesions managed by mainstream general practitioners and doctors within primary care skin cancer clinics.

Design, setting and participants: Prospective comparative study of 104 GPs and 50 skin cancer clinic doctors in south-eastern Queensland, involving 28 755 patient encounters. The study was conducted in 2005.

Main outcome measures: Prevalence of each type of skin lesion; sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the clinical diagnosis against histology; number needed to excise or biopsy (NNE) for a diagnosis of skin cancer.

Results: GPs excised or biopsied 3175 skin lesions (mean 2.5/week) including 743 basal cell carcinomas (BCCs) (23.4%), 704 squamous cell carcinomas (SCCs) (22.2%) and 49 melanomas (1.5%). Skin cancer clinic doctors excised or biopsied 7941 skin lesions (mean 34/week), including 2701 BCCs (34.0%), 1274 SCCs (16.0%) and 103 melanomas (1.3%). Overall, sensitivity for diagnosing any skin cancer was similar for skin cancer clinic doctors (0.94) and GPs (0.91), although higher for skin cancer clinic doctors for BCC (0.89 v 0.79; P < 0.01) and melanoma (0.60 v 0.29; P < 0.01). The overall NNE was similar for skin cancer clinic doctors (1.9; 95% CI, 1.8%-2.1%) and GPs (2.1; 95% CI, 1.9%-2.3%). This did not change after adjusting for years of clinical experience.

Conclusions: GPs and skin cancer clinic doctors in Queensland treat large numbers of skin cancers and diagnose these with overall high sensitivity. The two groups diagnosed skin cancer with similar accuracy.