* The PASI is an investigator-administered, multi-item scale used to measure the severity of psoriasis based on lesion severity and the percent of body surface area (BSA) affected. * Erythema, thickness, and scaling are scored on a scale of 0 (none) to 4 (very severe) on 4 anatomical regions: head, trunk, upper limbs, lower limbs. Degree of involvement on each of the 4 anatomic regions is scored on a scale of 0 (no involvement) to 6 (90% to 100% involvement). * The sum of severity scores for erythema, thickness, and scaling is multiplied by the degree of involvement for each anatomic region, and then multiplied by a constant corresponding to the region's percent BSA (0.1, 0.3, 0.2, and 0.4 for the above 4 regions, respectively). The resultant score for each anatomic region is then summed to yield the final PASI score. It ranges from 0 to 72, with higher scores reflecting greater disease severity. * The nonresponder imputation (NRI) method was used to handle missing data.