Validation of a novel high‐intensity LED light source for skin phototesting at 365 nm

Abstract

The gold standard for investigation of patients with suspected photosensitivity involves phototesting on non-exposed skin with an irradiation monochromator (IM). However, this device is bulky, expensive and only available at a small number of specialised photodermatology units. We have developed a small handheld high output monochromatic light source for phototesting to UVA at 365 nm using light-emitting diodes (LEDs). A UNO light engine (Enfis, Swansea, UK) at 365 nm was used to develop a handheld intense source. Seventy-seven normal healthy volunteers were phototested on the lower back with the LED source and with an IM at 365 nm. Minimal erythema dose (MED) at 24 h was assessed visually and by a diffuse reflectance erythemameter. In 77 volunteers, MED levels for the two sources agreed in 66 out of 77 cases (85.7%). In a further 10 out of 77 patients, the measured MED elicited by the LED source was 1 dose level higher than the monochromator MED. A high-intensity portable and low cost LED phototesting device was developed. The results confirm that phototesting to UVA at 365 nm using this LED light source compares favourably to monochromator light testing at this wavelength.