Skip to main content
. 2013 Jun 13;8(6):e65471. doi: 10.1371/journal.pone.0065471

Table 7. Effect of the intervention on imaging referral.

Variable Intervention group follow-up1 Control group follow-up2 Incident rate ratios3 (95% CI) p-value
No. referrals Rate/1000 patients No. referrals Rate/1000 patients
X-ray referral 643 8.3 768 10.2 0.83* (0.61, 1.12) 0.211
CT-scan referral 474 6.1 496 6.6 0.92 (0.66, 1.27) 0.598
X-ray or CT-scan referral 1117 14.4 1264 16.8 0.87 (0.68, 1.10) 0.244
1

No. Practices = 34 and No. GPs = 44; Total number of Medicare patients seen by GPs in intervention group = 77,716.

2

No. Practices = 37 and No. GPs = 40; Total number of Medicare patients seen by GPs in control group = 75,226.

3

Incident rate ratios estimated from negative binomial models fitted using GEEs with an exchangeable correlation structure and robust variance estimation to allow for clustering within general practices. For models where the estimated within cluster correlation was negative (indicated by*), the model was refitted assuming an independent correlation structure. All models adjusted for the design strata (number of GPs per practice, location of practice [metropolitan or rural/remote]) and confounders specified prior to undertaking the analysis (age of GP (years), years since GP graduated, special interest in LBP, practice method of billing [bulk bill or co-payment]).