Table 4

 Improvement definitions by the single domain disease activity measured by the Bath ankylosing spondylitis disease activity index and by the criteria of the Assessment in Ankylosing Spondylitis working group on different improvement levels

CriterionImprovement definitionInfliximab trialCombined dataset etanercept and infliximab trial (n = 69) (χ2)
Per cent improving in the placebo treated group (n = 35)Per cent improving in the infliximab treated group (n = 34)χ295% CI of the χ2 value
Columns 3–7: infliximab trial, week 12. Last column: data from the combined dataset at week 6; to be comparable, n = 69 from n = 98 at random. The criterion which performed best is shown in bold.
*Candidate criteria with χ2 values that are not significantly below reference criterion 1 (table 3).
†Placebo response significantly above 10%.
ASAS, Assessment in Ankylosing Spondylitis working group; BASDAI, Bath ankylosing spondylitis disease activity index; CI, confidence interval.
Relative improvement of disease activity
39⩾20% change of the BASDAI37.14†85.2916.794.72 to 32.0412.52
40⩾30% change of the BASDAI25.71†73.5315.783.68 to 30.8317.10
41⩾40% change of the BASDAI8.5764.7123.52*10.16 to 39.3021.31
42⩾50% change of the BASDAI8.5758.8219.60*7.46 to 34.0420.31
43⩾60% change of the BASDAI5.7138.2410.722.45 to 22.1915.67
44⩾70% change of the BASDAI5.7126.475.540.30 to 15.419.87
ASAS improvement criteria
45⩾20% and 10 units25.71†73.5315.784.41 to 30.7223.66
46⩾30% and 10 units11.4364.7120.85*8.59 to 36.9120.19
47 ⩾40% and 20 units 5.71 64.71 26.46* 13.30 to 41.14 17.34
48⩾50% and 20 units5.7152.9418.697.74 to 32.3915.01
49⩾60% and 30 units0.044.1219.7310.48 to 30.4513.88
50⩾70% and 30 units0.032.3513.476.07 to 22.565.38