Background: Ultraviolet (UV) B phototherapy is an established treatment option for psoriasis. The optimum dosage regimen still has to be determined. Within-subject comparisons do not take into account the systemic effects of UVB phototherapy. The area of the body treated with low-dose UVB may benefit from the systemic effects of the site treated with a higher UVB dose.
Objectives: To study the time to clearance in patients with psoriasis in a randomized controlled trial, in which patients were treated with narrowband UVB in either a high-dose or a low-dose regimen.
Methods: One hundred and nine patients were randomized to a high-dose regimen (group 1) or to a low-dose regimen (group 2). Patients of group 1 and 2 were irradiated with 40% and with 20% incremental doses, respectively, three times weekly. Psoriasis Area and Severity Index (PASI) was measured at baseline and at every 4-week control visit. Treatment was stopped in cases of clearance (90% reduction of baseline PASI).
Results: No significant differences were found in the number of patients achieving clearance. The high-dosage scheme resulted in four fewer treatments with no significant differences in cumulative UV dose, although more protocol adjustments were required in the beginning of the study because of erythema. After 3 months a significantly better clinical outcome was seen after high-dose UVB therapy.
Conclusions: High-dose UVB therapy results in fewer treatments with better long-term efficacy, with cost-effective benefits for hospital and patients. Therefore UVB phototherapy in a high-dose regimen for psoriasis is recommended. However, a protocol adjustment in the second week with a high-dose regimen is desirable to prevent erythema.