This might be because of the shorter treatment duration and the 22 lower dose of methotrexate. In our study, the followup sample was taken after 4 weeks of treatment of low-dose methotrexate (7.5 mg / week) and NBUVB while in the study of Phan Huy Thuc, patients were treated with the higher dose of methotrexate (15 mg / week) until achieving PASI 75.