Table 2

Measures of discrimination and responsiveness for changes in MRIa score according to different types of treatment response

MRIa score
Change from baseline to week 24 (n=158)*Change from baseline to week 102 (n=179)*
Mean (SD)Median (IQR)SRMΔSRMSMDF-score (p value)†AUC (95% CI)Mean (SD)Median (IQR)SRMΔSRMSMDF-score (p value)†AUC (95% CI)
ASDAS response‡
 No−2.3 (4.0)−1 (−4, 0)−0.56−2.3 (4.1)−1 (−5, 0)−0.57
 Yes (Δ ≥1.1)−4.3 (4.8)−3 (−8, 0)−0.90−0.34−0.456.4 (0.012)0.63 (0.54, 0.72)−5.0 (5.0)−4 (−8, −1)−0.99−0.42−0.5613.8 (<0.001)0.66 (0.58, 0.75)
BASDAI response‡
 No−2.6 (4.3)−1 (−4, 0)−0.60−3.1 (4.7)−1 (−5, 0)−0.66
 Yes (Δ ≥50% and/or Δ ≥2)−4.3 (4.7)−3 (−8, 0)−0.91−0.31−0.375.4 (0.022)0.61 (0.52, 0.70)−4.7 (4.9)−4 (−8, −1)−0.96−0.30−0.325.2 (0.023)0.61 (0.52, 0.70)
ASAS20 response‡
 No−3.1 (4.7)−2 (−5, 0)−0.66−3.2 (4.7)−2 (−6, 0)−0.68
 Yes (ASAS20)−4.0 (4.6)−2 (−8, 0)−0.88−0.22−0.191.5 (0.221)0.56 (0.47, 0.65)−4.6 (4.9)−3 (−8, −1)−0.93−0.25−0.294.8 (0.030)0.59 (0.49, 0.69)
  • ASAS20 response criterion is based on four independent domains: spinal pain, physical function measured by the Bath ankylosing spondylitis functional index, patient global assessment and inflammation measured as the mean of the last two BASDAI questions (severity and duration of morning stiffness); ASAS20 treatment response is defined as improvement of 20% or greater and 1 unit or greater (range 0–10) in at least three of the four above domains, and no worsening of 20% or greater and 1 unit or greater in the remaining fourth domain. BASDAI response is defined by at least 50% improvement or absolute improvement of at least 2 units on a 0–10 scale. ASDAS response is defined by an improvement of at least 1.1 units in ASDAS.

  • *Data are shown for the infliximab group at 24 weeks (placebo-controlled phase of the ASSERT trial) and for all patients at 102 weeks (open extension phase of the ASSERT trial).

  • †Results from analysis of variance on van der Waerden normal scores.

  • ‡Percentage of patients achieving a response at 24 weeks: ASDAS response, 69%; BASDAI response, 64%; ASAS20 response, 61%. Percentage of patients achieving a response at 102 weeks: ASDAS response, 73%; BASDAI response, 70%; ASAS20 response, 68%.

  • ASSERT, AS Study for the Evaluation of Recombinant Infliximab Therapy; ASDAS, ankylosing spondylitis disease activity score; AUC, area under the receiver operating characteristic curve; BASDAI, Bath ankylosing spondylitis disease activity index; SMD, standardised mean difference; SRM, standardised response mean.