Minimal Erythema Dose to Narrow Band Ultraviolet – B in a Group of Libyan Patients

Background: Narrow-band ultraviolet B (NBUV-B) is now widely considered as the first choice phototherapy modality for most photo-responsive skin conditions.In most dermatology centers where phototherapy is performed, the starting dose of NBUV-B phototherapy is calculated as a proportion of the minimal erythema dose (MED).This is in order to maximize the therapeutic response, decreasing therapeutic duration and reducing the risk of burning.Treatment with NBUV-B phototherapy is usually given three times per week, with a typical course requiring 18-30 treatments for disease clearance.Such treatment regimens require accurate assessment of the MED prior to commencing treatment in order to avoid overdoses or underdoes of NBUV-B.Aim: The purpose of this study is to determine the MED of 311nm NBUV-B in a group of Libyan patients.Methods: 150 patients with a various skin diseases who attending the phototherapy unit at Beer UstaMelad hospital of dermatology and venereology, Tripoli -Libya during an 8 months period were recruited for this prospective study.The studied skin diseases include psoriasis, vitiligo, atopic dermatitis and others.All patients were classified into skin types using the questionnaire of Fitzpatrick.Irradiation with 311nm NBUV-B was performed over the right forearm by using a MED tester device (Dermalight® 80 ) then the results of the test were recorded 24 hours later.Results: Among the studied patients; 82(54.7%)patients were females and 68(45.3%)patients were males.Their age ranged between 10 -60 years while 30% of the included group were in the age group of 31-40 years.The patients were diagnosed on clinical grounds to have the following conditions; vitiligo 65(43.3%)patients, psoriasis 61(40.7%)patients, eczema 8(5.3%) patients, pruritus 6(4%) patients and alopecia areata and lichen planus 5(3.3%) patients each .According to Fitzpatrick's classification, the skin phototypes of the included series were; 15(10%) patients of skin type III, 118 (78.7%) patients of skin type IV and 17(11.3%)patients of skin type V.The minimal required dose to produce an erythema for NBUV-B among the recruited patients was ranged between 300 mJ/cm2 to 750 mJ/cm2 with a mean dose of 484.7±82.2mJ/cm2 .Conclusions: The mean MED to 311nm NBUV-B in Libyan patients was around 500 mJ/cm2, and this can be used to decide the initial dose and treatment regimen of phototherapy for different skin diseases.