Similar dose-response and persistence of erythema with broad-band and narrow-band ultraviolet B lamps.
Psoriasis may be treated with ultraviolet B from lamps that have a broad emission spectrum or, more effectively, with lamps that have a narrow emission spectrum at 311 +/- 2 nm. There are conflicting reports of either greater or lesser burning episodes with narrow-band compared to broad-band ultraviolet B, even when treatments are based on predetermined minimal erythema dose measurements. This suggests that either the characteristics of the dose-response curve for erythema or the time course for erythema may be different for the two lamps. We examined the erythemal response to narrow-band and broad-band ultraviolet B in 12 patients with psoriasis. A geometric series of 10 doses from each lamp type were used on nonlesional skin on the back. Dose-response curves were constructed from reflectance measurements of erythema at 24 h and 72 h after irradiation. No significant difference was found in steepness of the erythema dose-response curve for the two lamps at 24 or 72 h. Persistence of erythema was assessed as the percentage of erythema remaining at 72 h. The mean persistence was 63% for narrow-band and 64% for broad-band lamps (p = 0.94). Therefore, in terms of erythemal response, no evidence has been found for a difference in burning potential for the two lamps.
Das
S
S
Department of Dermatology, Royal Victoria Infirmary, Newcastle upon Tyne, UK.
Lloyd
J J
JJ
Farr
P M
PM
D000328:Adult; D004307:Dose-Response Relationship, Radiation; D004890:Erythema / Q000209:etiology* / Q000473:pathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011832:Radiation Injuries; D013997:Time Factors; D014466:Ultraviolet Rays