A Randomized Comparison of Methods of Selecting Narrowband UV-B Starting Dose to Treat Chronic Psoriasis

Abstract

To compare narrowband UV-B (TL-01 lamp) phototherapy for psoriasis with individual patient starting doses based on minimal erythemal dose (MED) determination vs a standard fixed starting dose and to compare the efficacy of 70% of MED vs 50% of MED starting dose regimens. Single-center, randomized, double-blind, clinical trial. Department of Dermatology, Ninewells Hospital and Medical School, Dundee, Scotland. A total of 210 adult patients (207 of skin phototypes I to III) referred for narrowband UV-B to treat chronic psoriasis. The study was designed to have 90% power to detect a difference of 3 or more treatments to clearance and/or minimal residual activity (MRA) between groups. Narrowband UV-B phototherapy was given according to 3 standard regimens, differing only by starting dose selection method. The randomly allocated starting doses were (1) a fixed starting dose, (2) 70% of individual MED, and (3) 50% of individual MED. All patients were MED tested to ensure blinding and for safety reasons. The number of treatments to clearance and/or MRA of psoriasis was the primary efficacy outcome measure, with changes in Psoriasis Area and Severity Index and Psoriasis Disability Index scores as secondary measures. Adverse effects were recorded. There were no significant differences in the number of treatments to clearance and/or MRA across all 3 groups or in the percentages achieving clearance in each group. More uncomfortable erythemas occurred in the 50% of MED starting dose group (39%) than in the 70% of MED starting dose group (24%) or the fixed starting dose group (24%) (P=.07). The methods of determining the starting dose in this predominantly skin phototype I and II population, treated 3 times weekly, with a 20% followed by 10% incremental reduction in dose, did not significantly influence the effectiveness of treatment. Had there been a clinically important difference in efficacy, we would have expected to identify this. Thus, basing starting dose on individual MED assessments may not influence the treatment's efficacy in a skin phototype I to III population, although it remains important for patient safety. It remains possible that in populations containing individuals with a broader range of erythemal sensitivity, basing the starting dose on MED testing could have an important impact on treatment effectiveness. isrctn.org Identifier: ISRCTN84614024.