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Table 3 Results of the logistic regression

From: Printed educational messages fail to increase use of thiazides as first-line medication for hypertension in primary care: a cluster randomized controlled trial [ISRCTN72772651]

Regression model 1a: unadjusted effect of interventions, insert and combined outserts
Intervention Odds ratio 95 % confidence interval p value
informed only (reference group) 1.00   0.54
 + insert 0.97 0.86 to 1.09  
 + outsert 0.93 0.83 to 1.05  
 + insert and outsert 1.01 0.90 to 1.14  
Regression model 1b: effect of interventions, adjusted for patient and physician covariates, insert and combined outsertsa
Intervention Odds ratio 95 % confidence interval p value
informed only (reference group) 1.00   0.60
 + insert 0.98 0.87 to 1.11  
 + outsert (combined) 0.93 0.83 to 1.05  
 + insert and outsert 1.00 0.89 to 1.12  
Effect of patient and physician characteristicsb
Physician characteristics
 Female (reference is male) 1.27 1.14 to 1.40 <0.0001
Place of training    <0.0001
 Canada (reference) 1.00   
 USA 0.90 0.77 to 1.06 0.21
 UK, Ireland, Australia, New Zealand 0.75 0.43 to 1.30 0.30
 Other 0.53 0.46 to 0.61 <0.0001
Group practice (reference is solo practice) 1.21 1.10 to 1.32 <0.0001
Rural (reference is non-rural) 1.39 1.23 to 1.57 <0.0001
Years since graduation (odds ratio per additional 10 years) 1.06 1.01 to 1.11 0.014
Elapsed time between mail-out and patient visit (odds ratio per additional 30 days) 0.98 0.97 to 0.99 <0.0001
Patient characteristics
Female sex (reference is male) 1.37 1.29 to 1.45 <0.0001
Age (odds ratio per additional 10 years of age) 1.09 1.05 to 1.14 <0.0001
Location of the visit    <0.0001
 Physician office (reference) 1.00   
 Long-term care 0.68 0.56 to 0.84 0.0002
 Patient’s home 0.96 0.68 to 1.35 0.81
 Phone call 0.30 0.13 to 0.70 0.0050
Regression model 2a: unadjusted effect of interventions, with outserts split by type
Intervention Odds ratio 95 % confidence interval p value
informed only (reference group) 1.00   0.69
 + insert 0.97 0.86 to 1.09  
 + atheoretical outsert 0.95 0.82 to 1.09  
 + TPB-based outsert 0.92 0.80 to 1.06  
 + insert and atheoretical outsert 0.97 0.84 to 1.12  
 + insert and TPB-based outsert 1.05 0.91 to 1.21  
Regression model 2b: effect of interventions, adjusted for patient and physician covariates, insert and outserts split by type
Intervention Odds ratio 95 % confidence interval p value
informed only (reference group) 1.00   0.71
 + insert 0.98 0.87 to 1.11  
 + atheoretical outsert 0.94 0.81 to 1.08  
 + TPB-based outsert 0.93 0.81 to 1.07  
 + insert and atheoretical outsert 0.96 0.83 to 1.10  
 + insert and TPB-based outsert 1.05 0.91 to 1.21  
  1. aThe model was adjusted for these patient variables: age, sex and location of the visit with the physician. The model was adjusted for these physician variables: year of graduation, sex, place of training, type of practice (solo/group), place of practice (rural/urban) and elapsed time between the mail-out and the office visit
  2. bOdds ratios are adjusted for all of the other variables in the model
  3. p values for interactions with the intervention
  4. Informed subscriber p = 0.73
  5. Rural location p = 0.97
  6. Practice type, p = 0.88
  7. Patient sex, p = 0.81
  8. Location of visit, p = 0.76
  9. Patient age, p = 0.58
  10. GP sex, p = 0.36
  11. Number of years since GP graduation, p = 0.29
  12. Graduation place, p = 0.18
  13. Time from mail-out to patient visit, p = 0.15
  14. p value for four-level intervention = 0.60
  15. p value for six-level intervention = 0.71
  16. All of the main effects are significant