Percentage of patients in each study group who had a treatment response. A treatment response was defined as 20% or greater improvement in at least three of five outcome measures (duration of morning stiffness, degree of nocturnal spinal pain, the Bath Ankylosing Spondylitis Functional Index, the patient's global assessment of disease activity, and the score for joint swelling). The patients in the etanercept group received etanercept throughout the 10-month study period; those in the placebo group received placebo for 4 months, followed by etanercept for 6 months. The differences between the groups were statistically significant at month 1 (P < 0.001), month 3 (P = 0.03), and month 4 (P = 0.004). During the open-label portion of the trial, there were no statistically significant differences between the two groups. Reproduced with permission from . Copyright © 2002 Massachusetts Medical Society. All rights reserved. Note that subsequent reanalysis of the data the end of 4 months corrected the P value to 0.001 .