Skin reflectance-guided UVB phototherapy of psoriasis reduces the cumulative UV dose significantly

Design and evaluation of a novel portable erythema-melanin-meter

BACKGROUND AND OBJECTIVES

Objective evaluation of the pigmentation index (PI) and the eythema index (EI) of human skin is a prerequisite for successful optimization of laser- and intense-pulsed-light (IPL)-based treatment modalities in dermatology.

STUDY DESIGN/MATERIALS AND METHODS

We describe a three-wavelength technique for determining PI and EI as well as its particular implementation using LEDs operating at wavelengths of 560, 650, and 710 nm and a large-area photodiode. The instrument has been evaluated both in vitro and in vivo.

RESULTS

In vitro, good correlation between the measured indices and results obtained with commercially available techniques has been observed. In addition, linearity of the PI with melanin concentration in the phantom medium up to 7 x 10(-3) nm(-1) (defined as a slope of the optical density spectrum) has been established. In vivo, feasibility of using the technique for predicting the minimal erythema dose (MED), minimal phototoxic dose (MPD), and the threshold of epidermal damage in a photothermal treatment has been demonstrated.

CONCLUSIONS

The data suggest that the technique has a substantial potential as a method of pre-treatment diagnostics for photochemical and photothermal procedures.

Optimized UVB treatment of psoriasis: a controlled, left-right comparison trial

In a randomized, controlled, left-right comparison study, 20 patients with chronic plaque psoriasis were treated with UVB. One side of the body received UVB in a conventional regimen with fixed dose increments, the other side was given UVB doses according to measurements of skin pigmentation. Skin pigmentation was quantified by the skin reflectance technique. The relationship between skin pigmentation and sensitivity to UV radiation was used to optimize and individualize the initial UVB exposure dose. Clinical outcome, initial, final and cumulative UVB doses, time to 50% reduction in PASI score, and side-effects were compared. The consequence of the optimization of the UVB doses with a skin reflectance meter was that the initial UVB dose was significantly higher than in the conventional UVB regimen. PASI scoring demonstrated a more rapid improvement during the first 2 weeks of treatment on the half body receiving the optimized treatment compared to the other side (P < 0.05). This new technique offers the same therapeutical advantages and security as a dose regimen guided by minimal erythema dose testing. However, measurement of skin pigmentation by skin reflectance is a quick method which can be operated easily by nurses.