MedWire News: Determining the appropriate dose of narrowband ultraviolet-B (NB-UV-B) treatment for psoriasis patients by first working out their minimal erythemal dose (MED) does not affect treatment efficacy, but is important for identifying adverse effects, say researchers.
Their findings show no significant difference in the number of treatments to clearance or minimal residual activity (MRA) between patients receiving a standard starting NB-UV-B dose, compared with those whose initial NB-UV-B dose was 50% or 70% of MED.
However, one patient was discovered to have previously unsuspected severe photosensitivity due to chronic actinic dermatitis "and would likely have had a severe reaction had we not conducted MED testing," say Robert Dawe (Ninewells Hospital and Medical School, Dundee, Scotland) and co-workers.
This "emphasizes the need for some form of small area testing before proceeding with whole-body NB-UV-B," they write, in the Archives of Dermatology.
A total of 210 patients with chronic psoriasis (skin phototypes I to III) were randomly assigned to receive either a fixed non-MED-based starting dose of 140 mj/cm2 (n=70), 70% of individual MED (n=70), or 50% of MED (n=50). All patients were MED tested to ensure blinding and safety.
The median numbers of NB-UV-B treatments needed to achieve the primary outcome measure of clearance and/or MRA were 32 for the non-MED-based starting dose, 31 for the 70% MED group, and 29 for the 50% MED group, all nonsignificant differences.
Similarly, there were no large differences in time to primary outcome between treatment groups, with medians of 88 days for the non-MED-based starting dose group, 78 days for the 70% MED group, and 81 days for the 50% MED group.
In terms of adverse effect outcomes, grade 2 (well-demarcated, uncomfortable) or worse (grade 3 [painful] or 4 [painful with blistering]) erythema was reported at least once by 24% of those in each of the non-MED-based and 70% MED start groups, and 39% of the 50% MED start group.
"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," conclude Dawe et al.
This was highlighted during the initial MED-testing phase, when one patient - treated with a non-MED start dose - displayed an MED below the lowest initial MED test dose (25 mj/cm2), which caused erythema and edema at the test site.
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