A device for phototesting patients before PUVA therapy

Abstract

A device is described and validated for rapid and easy phototesting of patients at the start of a course of PUVA therapy. The phototesting template consists of metal foil with four apertures of 10 mm diameter, mounted in pliable polyurethane. One aperture is open, and the other three each incorporate a grid of hexagonal holes of differing size which attenuate the radiation, resulting in relative intensities at the skin surface of 1, 2, 4 and 8. Thus, a single exposure through the foil of, for example, 8 J/cm2, would allow the minimal phototoxic dose to be determined as either 1, 2, 4, 8, or > 8 J/cm2. The device was validated by comparison with a metal foil with four open apertures, but otherwise identical construction, in which the dose was controlled by varying the exposure time. In 11 subjects, tested with one device on each arm, the minimal phototoxic dose, judged visually, was identical. Reflectance measurements of erythema at each of the test sites showed no systematic difference between the two methods. The device has no moving parts, requires no source of electrical power, will not change its optical transmission with age, and is robust and easy to use. It should, therefore, allow much wider application of the useful technique of minimal phototoxic dose determination before PUVA therapy.

Phototesting prior to narrowband (TL‐01) ultraviolet B phototherapy

“…9 As designed for PUVA phototesting, the template was placed on the skin, usually on the arm, which was then exposed to an appropriate UVA source, using a cotton sleeve to prevent exposure of the skin surrounding the template. The use of a variably perforated metal foil in conjunction with a fluorescent UV lamp to achieve a range of doses was first described for phototesting prior to PUVA therapy, and the technique has been fully validated.…”

“…The principle of the attenuator design, originally developed for phototesting prior to PUVA therapy, where an increment factor of two per aperture was used, has been described in detail previously. 9 The phototesting unit also contained a digital electronic integrating dose meter which switched off the lamp when the desired dose at the open aperture had been delivered. This arrangement avoided the need to allow the lamp to warm up fully to a stable, measured irradiance before use, and took account of diminishing output with lamp age.…”

Normalized ultraviolet (UV) induction of Langerhans cell depletion and neutrophil infiltrates after artificial UVB hardening of patients with polymorphic light eruption.

“…For determination of the MED, a phototesting device designed by Diffey et al was purchased from P.J. Saunders, Regional Medical Physics Department, University Hospital of North Durham, Durham, U.K. 23,24 This device is made of two flexible metal foils, containing 10 mesh attenuators giving 10 irradiance levels with increment steps of 26%, resulting in a 8 : 1 ratio from the highest to the lowest exposure. The device was slightly modified to maintain a constant distance of 3 mm from the skin.…”

Is disturbed clearance of apoptotic keratinocytes responsible for UVB-induced inflammatory skin lesions in systemic lupus erythematosus?

“…A Diffey grid [21] was used to irradiate the skin with 10 different doses (0.026 to 0.200 J/cm 2 ) during one exposure. After 24 hours, MED was determined by two independent observers, with more than 90% agreement.…”