Evaluation of a novel skin tone meter and the correlation between Fitzpatrick skin type and skin color

Abstract

Abstract Background and objective: To evaluate a novel skin tone meter (STM) to categorize skin tones into one of the six categories of the Fitzpatrick skin type (FST) classification system, thus optimizing safety in light-based dermatological procedures. This numerical classification method measures several components; principally the reaction of human skin to ultraviolet (UV) light exposure, which is used to help predict skin response in laser and intense pulsed light (IPL) treatments. Materials and methods: Two-hundred twenty volunteers of varying ethnic origin, age and gender were enrolled in a preliminary study. The subjects’ Fitzpatrick skin type was ascertained by a standardized questionnaire that determined their reaction to significant sunlight exposure. A calibrated prototype STM device (consisting of an optical head at 460 nm, detector, microprocessor, and a liquid crystal display) was used to measure the subjects’ inner arm skin; which typically has little UV exposure and minimal hair, and compared the obtained value with measurements taken from a skin color chart and digital photographs. To evaluate device performance (within subject) across different skin states, a section of skin from the inner arm of a sub-group of eight volunteers was marked into test areas using a template. The skin in each area was then prepared (i) with a control area, (ii) by degreasing with acetone for 1 min to represent dry skin, (iii) with a fine layer of coupling gel to represent hydrated skin, (iv) with a thin layer of petrolatum (Vaseline) to represent oily skin, and (v) with saline solution applied then dried to represent dried perspiration. Results: There was a consistent trend between the STM prototype and the assessed skin tone derived from a proprietary skin color chart against the measurement on skin across a range of skin conditions. Conclusion: The presented preliminary study demonstrated the subjective nature of the FST classification system and the weakness of skin tone self-assessment by an individual, as judged by expert assessors. The FST classification requires an objective measurement to replace the textual description for each skin tone. It may significantly decrease the risk of potential side effects through overtreatment, and extend treatment to a wider patient population with light-based dermatological procedures.