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Table 4 ITT and CACE model estimates of treatment difference at 3, 6 and 12 months

From: Treatment compliance and effectiveness of a cognitive behavioural intervention for low back pain: a complier average causal effect approach to the BeST data set

  ITT covariate model Standardised effect at 12 months† CACE covariate model Standardised effect at 12 months‡
  Mean treatment difference (95% CI)* p value Mean treatment difference (95% CI)† p value
Roland Morris Questionnaire (points)
3 months 1.1 (0.39, 1.77) 0.002 .. 1.1 (0.04, 2.22) 0.042 ..
6 months 1.4 (0.72, 2.16) <0.001 .. 1.9 (0.87, 2.98) <0.001 ..
12 months 1.3 (0.55, 2.07) 0.001 0.31 1.6 (0.51, 2.74) 0.004 0.43
Modified Von Korff disability (%)
3 months 4.6 (0.75, 8.52) 0.029 .. 5.4 (-0.38, 11.15) 0.067 ..
6 months 8.3 (4.32, 12.35) <0.001 .. 11.1 (5.30, 16.83) <0.001 ..
12 months 8.6 (4.58, 12.64) <0.001 0.42 12.1 (6.07, 18.17) <0.001 0.60
Modified Von Korff pain (%)
3 months 6.9 (3.53, 10.29) <0.001 .. 8.8 (3.84, 13.82) 0.001 ..
6 months 8.2 (4.48, 11.97) <0.001 .. 11.2 (5.89, 16.61) <0.001 ..
12 months 7.00 (3.26, 10.74) <0.001 0.37 10.4 (4.64, 16.10) <0.001 0.60
EQ-5D
3 months 0.08 (0.033, 0.117) <0.001 .. 0.09 (0.020, 0.161) 0.012 ..
6 months 0.04 (-0.007, 0.080) 0.098 .. 0.06 (-0.011, 0.121) 0.102 ..
12 months 0.05 (0.010, 0.097) 0.015 0.13 0.07 (0.008, 0.141) 0.029 0.36
  1. *Based on a linear regression model adjusted for age, sex, severity of back pain, centre and baseline value.
  2. †Based on a latent class model with outcome adjusted for age, sex, severity of back pain, centre and baseline value and compliance adjusted for age and baseline modified Von Korff pain score.
  3. ‡Standardised effect size is the unadjusted mean difference (standardised mean difference) between the groups divided by the pooled SD at baseline.