Clinical and genetic factors affect NB-UVB clearance, remission
MedWire News: Both genetic and clinical parameters are important in determining the number of exposures of narrow-band ultraviolet B (NB-UVB) needed to clear psoriasis and the duration of remission, researchers report.
"As NB-UVB treatment is time consuming, expensive, and potentially carcinogenic, the ability to predict patients who will clear quickly with prolonged remission would be useful," say Catriona Ryan, from St Vincent's University Hospital in Dublin, Ireland, and colleagues.
They used NB-UVB to treat 119 patients with chronic plaque psoriasis until clearance was achieved and then monitored the patients for up to 1 year or until relapse occurred.
In all, 105 of the patients completed the course of phototherapy and using an intention-to-treat analysis 83% of the initial cohort achieved clearance after a median of 26 exposures and the median remission duration was 16 weeks.
The researchers found that patients needed fewer NB-UVB exposures to achieve clearance the less severe their psoriasis before treatment (as indicated by baseline Psoriasis Area and Severity Index score), the better their quality of life (as indicated by baseline Dermatology Life Quality Index [DLQI] score), the more previous courses of NB-UVB they had received, and if they were women and had low body weight.
They note that weight was more important than gender in predicting clearance. After adjusting for gender, each kg increase in weight corresponded to a 1.4% decrease in the likelihood of clearance.
Patients whose condition cleared quickly had a significantly longer duration of remission than patients whose condition took longer to clear, and this was the only clinical parameter predicting remission duration.
The Taq1 polymorphism of the vitamin D receptor gene (VDR) also predicted remission duration, however, with patients homozygous for the C allele, which is associated with a decreased activity of VDR, remitting sooner than those heterozygous for the allele or homozygous for the T allele.
"Patients homozygous for the T allele were only 48% as likely as those homozygous for the C allele to relapse," the researchers report in the British Journal of Dermatology.
They conclude: "This study provides a paradigm for other studies, highlighting the need to assess both clinical and genetic factors when assessing treatment outcomes in psoriasis."
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By Lucy Piper