Quantifying actinic keratosis: assessing the evidence.

Actinic keratoses are pre-malignant lesions, and it is standard practice to destroy them. Optimal management of actinic keratoses requires data on the efficacy of the numerous techniques employed in their treatment. Evaluating treatment efficacy requires before and after treatment quantification of actinic keratoses. Studies on the therapy and natural history of actinic keratoses have quantified these lesions by counting them. Counting actinic keratoses is unreliable because this technique lacks interobserver reproducibility. Consequently, studies based on counting actinic keratoses are fatally flawed and their conclusions of doubtful accuracy. Counting actinic keratoses should be abandoned as a technique for evaluating the therapy of actinic keratoses and the issue of spontaneous regression of actinic keratoses. A technique for reliably quantifying actinic keratoses is sorely needed.