Photodynamic Diagnosis of Actinic Keratosis: A Systematic Review.

Actinic keratosis (AK) is a precancerous condition typically diagnosed by hyperkeratotic papules. The concept of field cancerization suggests subclinical lesions surround visible actinic keratoses. Photodynamic diagnosis (PDD)is a non-invasive imaging modality that can im-prove actinic keratosis diagnosis and treatment assessment. This systematic review describes current evidence regarding photodynamic diagnosis modalities for actinic keratosis. We searched MEDLINE and Embase through 28 February, 2025. Data synthesis was descriptive due to methodological heterogeneity across studies. Thirty-seven studies were included. Methyl aminolevulinate(MAL) and aminolevulinic acid (ALA)were used in 54% and 51% of studies, respectively. Incubation times ranged from 20 to 1080 min, 70 % of studies followed a 3 -h protocol. Most excitation sources (89%) emitted light within the 400-410 nm range, often via clinical-grade systems (54%). Imaging hardware varied: 54 % used integrated clinical systems, 30 % used independent cameras. Fluorescence quantification was described in 62 % of studies, and 54 % used specialized analysis software. Patient positioning was rarely reported (8%). This review highlights significant methodological heterogeneity in actinic keratosis photodynamic diagnosis, particularly in photosensitizer protocols and imaging systems. While clinical-grade systems provide standardization, low-cost alternatives enhance accessibility. However, lack of procedural consistency limits comparability. Future efforts should focus on advancing standardized protocols to support broader clinical validation and adoption.