A randomized comparison of methods of selecting narrowband UV-B starting dose to treat chronic psoriasis.

Objectives: 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.

Design: Single-center, randomized, double-blind, clinical trial.

Setting: Department of Dermatology, Ninewells Hospital and Medical School, Dundee, Scotland.

Patients: 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.

Interventions: 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.

Main Outcome Measures: 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.

Results: 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).

Conclusions: 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.

Trial Registration: isrctn.org Identifier: ISRCTN84614024.