Clinical evaluation of acne by cross polarizing photography

Background: Photography is one of the most objective methods in the clinical evaluation of acne. To standardize the quality of photographs, it is essential to standardize variables including focus distance, exposure time, posture and removal of flash glare but this is still insufficient. Cross polarizing photography (CPP) with a stereotactic device (STD) is a possible solution. Objective: This study was conducted to determine the feasibility of photographic assessment using CPP with STD instead of direct inspection in Korean acne patients. Methods: Sixty patients with acne (mean age=23.4, M=29, F=31) were enrolled in this study. Pictures using CPP with STD were taken three times during a 4-week period. Inflamed acne lesions that were counted at each visit were compared to the photographic assessment in a double-blind manner. To assess the quality of the picture, conventional photographs using a digital camera were also taken. Results: The coefficient of correlation between direct lesionai counting and photographic counting was 0.80. Photographic counting showed slightly higher results than direct counting. There was also a high coefficient of correlation (ranging from 0.78 to 0.85) among the inter-rater correlation which was 0.92. Photographs taken by CPP with STD showed an excellent quality in evaluating inflamed lesions of acne. Reduced glare and exact posture allowed for the detection of subtle lesions, that could not be seen in conventional pictures. Conclusion: Photography using CPP with STD is an objective, convenient and reproducible method for Korean acne patients. This method can be applied in evaluation of therapeutic response in clinics and clinical studies.