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Table 5 CACE model estimates of treatment difference with re-defined compliance

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

  Assessment only 1 or more group sessions 2 or more group sessions
  Mean treatment difference (95% CI)* p value Standardised effect at 12 months‡ Mean treatment difference (95% CI)* p value Standardised effect at 12 months‡ Mean treatment difference (95% CI)* p value Standardised effect at 12 months‡
Roland Morris Questionnaire (points)      
3 months 1.1 (0.30, 1.86) 0.007 .. 0.8 (-0.10, 1.72) 0.079 .. 1.1 (0.07, 2.09) 0.035 ..
6 months 1.4 (0.59, 2.18) 0.001 .. 1.7 (0.80, 2.60) <0.001 .. 1.8 (0.78, 2.74) <0.001 ..
12 months 1.4 (0.61, 2.25) 0.001 0.34 1.5 (0.55, 2.43) 0.002 0.38 1.5 (0.48, 2.56) 0.004 0.40
Modified Von Korff disability (%)      
3 months 4.9 (0.61, 9.14) 0.025 .. 4.6 (-0.27, 9.43) 0.064 .. 5.1 (-0.24, 10.38) 0.061 ..
6 months 8.7 (4.34, 13.07) <0.001 .. 9.6 (4.71, 14.53) <0.001 .. 10.3 (4.97, 15.65) <0.001 ..
12 months 9.4 (4.93, 13.78) <0.001 0.46 10.3 (5.19, 15.35) <0.001 0.52 11.1 (5.57, 16.71) <0.001 0.56
Modified Von Korff pain (%)      
3 months 7.2 (3.53, 10.93) <0.001 .. 7.5 (3.37, 11.73) <0.001 .. 8.2 (3.57, 12.78) <0.001 ..
6 months 8.7 (4.59, 12.76) <0.001 .. 9.7 (5.10, 14.29) <0.001 .. 10.4 (5.43, 15.40) <0.001 ..
12 months 7.9 (3.69, 12.03) <0.001 0.43 8.8 (3.99, 13.58) <0.001 0.50 9.4 (4.08, 14.66) 0.001 0.53
EQ-5D       
3 months 0.1 (0.01, 0.11) 0.015 .. 0.1 (0.02, 0.14) 0.014 .. 0.1 (0.01, 0.14) 0.024 ..
6 months 0.04 (-0.01, 0.09) 0.12 .. 0.04 (-0.01, 1.00) 0.128 .. 0.1 (-0.01, 0.11) 0.102 ..
12 months 0.1 (0.04, 0.13) <0.001 0.40 0.1 (0.01, 0.12) 0.022 0.32 0.1 (0.01, 0.13) 0.023 0.36
  1. CACE model estimates at 3, 6 and 12 months with compliance re-defined as attendance at the individual assessment only, attendance at the individual assessment and one or more group therapy sessions and two or more group therapy sessions.
  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 with the exception of modified Von Korff pain score at 6 months where compliance is only adjusted for age.
  3. The number of participants used in the regression analyses differs for each month on each score; due to missing data in the outcome and predictors.
  4. ‡Standardised effect size is the unadjusted mean difference (standardised mean difference) between the groups divided by the pooled SD at baseline.