Response of psoriasis to sunbed treatment: comparison of conventional ultraviolet A lamps with new higher ultraviolet B-emitting lamps.

BACKGROUND

Sunbeds fitted with conventional ultraviolet (UV) A lamps that have about 0.7% UVB emission are widely used by patients with psoriasis even though they are minimally effective. A new fluorescent sunbed lamp has been developed that emits a higher proportion of UVB (4.6%) than conventional lamps and also requires shorter exposure times to achieve equivalent erythema.

OBJECTIVES

To perform a randomized, within-patient comparison of conventional sunbed lamps (Cleo Performance) with the new lamps (Cleo Natural) in the treatment of psoriasis.

METHODS

A sunbed and canopy unit were modified to allow exposure to Cleo Performance lamps on one side of the body (front and back) and Cleo Natural lamps to the other side of the body. Two studies were done. In study 1, equal erythemal doses were given from the two lamp types. In study 2, equal exposure times were given. We treated 34 patients with psoriasis, giving 12 exposures over a period of 4 weeks. Assessment was made using a modified Psoriasis Area and Severity Index (PASI) score, individual plaque assessment and patient questionnaire.

RESULTS

Fourteen patients completed each study. In study 1, there was no significant difference in median improvement in half-body PASI score for the two lamp types. In study 2, there was a significant difference in PASI score improvement between the two lamps (median Cleo Performance change minus median Cleo Natural change was - 2.20; 95% confidence interval - 3.75 to - 0.65; P = 0.006).

CONCLUSIONS

That no difference in response was found when equal erythemal doses were given suggests that the spectral emission of the Cleo Natural lamp is of no greater advantage for clearance of psoriasis than conventional lamps. However, the Cleo Natural lamps are more erythemally powerful, and exposure times similar to those used in conventional sunbeds result in a significant improvement of psoriasis. The risk of non-melanoma skin cancer from different patterns of exposure to Cleo Natural lamps can be estimated using established numerical models.