Primary care clinicians' performance for detecting actinic keratoses and skin cancer

Background: If skin cancer screening is to become widely adopted, its effectiveness depends on the ability of primary care clinicians to detect cutaneous malignancies. Objective: To assess primary care clinicians' proficiency for detecting skin cancers and actinic keratoses in a clinic population. Methods: A convenience sample of 190 white male patients aged 40 years or older presenting to a university-affiliated Veterans Affairs general internal medicine or dermatology clinic were included in the study. Each patient was independently examined by a primary care clinician and a dermatologist to measure interobserver agreement. We compared the ability of primary care clinicians in diagnose actinic keratoses and skin cancers using dermatologists' examinations as a pragmatic reference standard. Results: Agreement was moderate as to whether a patient had single actinic keratosis (κ, 0.36; 95% confidence interval [CI] 0.22-0.50), multiple actinic keratoses (κ, 0.48; 95% CI, 0.34-0.61), or skin cancer (κ, 0.48; 95% CI, 0.34-0.62). Agreement decreased when individual lesions were the unit of analysis. When the patient was the unit of analysis, primary care clinicians identified the presence of skin cancer with a sensitivity of 57% (95% CI, 44%-68%), specificity of 88% (95% CI, 81%-93%), positive likelihood ratio of 4.9 (95% CI, 3.0-8.3), and negative likelihood ratio of 0.48 (95% CI, 0.350.63). When the lesion was the unit of analysis the sensitivity was 38% (95% CI, 29%-47%), the specificity was 95% (95% CI, 93%-96%), the positive likelihood ratio was 7.1 (95% CI, 4.8-10.3), and the negative likelihood ratio was 0.66 (95% CI, 0.56-0.75). Conclusions: Examinations performed by primary care clinicians for diagnosing skin cancer lacked sensitivity. Without improved diagnostic skills, primary care clinicians' examinations may be ineffective as a screening test.