Dramatic impact of a Psoriasis Area and Severity Index 90 response on the quality of life in patients with psoriasis: an analysis of Japanese clinical trials of infliximab.

European S3 Guidelines on the systemic treatment of psoriasis in 2009 propose 75% or more improvement in the Psoriasis Area and Severity Index from baseline (PASI 75) and a Dermatology Life Quality Index (DLQI) of 0 or 1 as treatment goals. However, the relationship of these two parameters is yet to be clarified. Herein, we analyzed the data pooled from two Japanese phase III clinical trials on psoriasis with infliximab to clarify the PASI response necessary to achieve a DLQI of 0 or 1. Of the 90 patients, the mean percent improvement in PASI at week 50 or 66 was 74.5%, and the PASI 75 and PASI 90 response rates were 66.7% and 46.7%, respectively; no difference in the improvement was noted among the body areas. Significant improvements in nail psoriasis were also observed. A negative correlation was shown between the improvement in PASI and DLQI. Patients who achieved a PASI 90 response had a significantly higher percentage of achieving a DLQI of 0 or 1 than the patients who achieved a PASI 75 but not a PASI 90 response. The median serum trough level of infliximab was maintained at 2 μg/mL or more in the PASI 90 responders, whereas it was less than 1 μg/mL at week 30 and on in the others. The present results demonstrate that a PASI 90 response is necessary to achieve a DLQI of 0 or 1. Infliximab is considered a useful drug in meeting the treatment goal of achieving a DLQI of 0 or 1 through the attainment of a PASI 90 response.