Far erythemogenic NB-UVB dose effective for plaque-type psoriasis
MedWire News: Far erythemogenic dose of narrow-band ultraviolet B (NB-UVB) phototherapy appears to be as effective as near and suberythemogenic doses for plaque-type psoriasis, say researchers.
Most studies of NB-UVB have used near erythemogenic (70% minimal erythematous dose [MED]) or sub-erythemogenic (50% MED) doses, but there are some concerns regarding the long-term risk for premature aging or photocarcinogenesis with such treatment, note Rutsanee Akaraphanth and colleagues from Medical Services in Bangkok, Thailand.
Although unable to confirm it in their study, the researchers suggest that using far erythemogenic (35% MED) doses of NB-UVB may be a better option than higher MED starting doses in terms of cumulative UV irradiation.
The team treated 50 patients with chronic plaque-type psoriasis using far erythemogenic dose NB-UVB 3 days a week. Most of the patients had skin type IV and their MED ranged from 570–800 mJ/cm2.
The average starting dose was only 231 mJ/cm2 and the dose was increased by 20% and then reduced in 10% increments at each visit depending on the individual’s erythema response.
The average Psoriasis Area and Severity Index (PASI) score at baseline was 13.57, and this decreased to 8.98 and 4.49 by the 12th and 30th sessions, respectively.
The researchers note in The Journal of Dermatology that 42% of patients achieved a 75% improvement in PASI score by the end of treatment and 36% achieved a 50% improvement.
The clearance rate of the patients was 68% after 30 treatment sessions, which Akaraphanth and colleagues say compares favorably with previous findings for NB-UVB treatment at 70% MED.
In addition to the clinical improvement, patients showed a marked improvement in quality of life (QoL) after treatment with far erythemogenic dose NB-UVB, with an average 79.7% improvement in scores on the Dermatology Life Quality Index.
While the clinical severity of psoriasis and QoL did not correlate at baseline, QoL correlated with the extent of psoriasis improvement after NB-UVB phototherapy.
This suggests that “with the treatment we provided, the QoL was more related to recent changes in psoriasis severity than to the severity of psoriasis itself,” the researchers comment.
They conclude: “Far erythemogenic doses of NB-UVB are considered to be as effective as near erythemogenic doses (75% MED) or sub-erythemogenic doses (50% MED) for plaque type psoriasis.
“It can decrease the disease severity and improve QoL in a vast majority of patients.”
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By Lucy Piper