Table 3. Subgroup analyses comparing changes in prescription rates of PIPs by the seven GP-related characteristics. Unadjusted IRRs and their 95% CIs obtained from the Poisson regression model with cluster effects at CME group level showing the changes in PIPs within the subgroups, α = 0.007.

Subgroups	Intervention group		Control group
	IRR (95% CI)	P-value	IRR (95% CI)	P-value
Age group, years
27–42	0.92 (0.85 to 0.99)	0.043	1.12 (1.04 to 1.21)	0.004
43–48	0.78 (0.72 to 0.82)	<0.007	0.89 (0.84 to 0.95)	0.001
49–52	0.81 (0.77 to 0.86)	<0.007	0.83 (0.77 to 0.90)	<0.007
53–56	0.81 (0.83 to 0.85)	<0.007	0.92 (0.86 to 0.98)	0.006
57–68	0.77 (0.73 to 0.81)	<0.007	0.92 (0.87 to 0.97)	0.003
Specialist
Non-specialist	0.84 (0.77 to 0.93)	<0.007	1.04 (0.96 to 1.13)	0.329
Specialist	0.80 (0.78 to 0.82)	<0.007	0.91 (0.88 to 0.94)	<0.007
Type of practice
Single-handed	0.75 (0.68 to 0.83)	<0.007	0.91 (0.83 to 0.99)	0.034
Group	0.80 (0.78 to 0.83)	<0.007	0.93 (0.90 to 0.96)	<0.007
Sex
Female	0.85 (0.80 to 0.90)	<0.007	0.93 (0.88 to 0.99)	0.027
Male	0.79 (0.77 to 0.81)	<0.007	0.92 (0.89 to 0.95)	<0.007
Practice setting
Rural	0.80 (0.77 to 0.83)	<0.007	0.92 (0.88 to 0.96)	<0.007
Urban	0.80 (0.78 to 0.83)	<0.007	0.93 (0.90 to 0.97)	<0.007
Mean PIPs per 100 prescriptions 1 year pre-intervention
≤1.6	0.88 (0.81 to 0.95)	0.001	1.09 (1.00 to 1.18)	0.041
1.7–2.0	0.83 (0.78 to 0.88)	<0.007	1.04 (0.97 to 1.12)	0.265
2.1–2.3	0.81 (0.76 to 0.85)	<0.007	0.85 (0.80 to 0.90)	<0.007
2.4–2.9	0.74 (0.70 to 0.78)	<0.007	0.89 (0.84 to 0.93)	<0.007
>2.9	0.80 (0.76 to 0.83)	<0.007	0.89 (0.83 to 0.96)	0.004
Prescriptions per patient in the 1 year pre-intervention period
<8.7	0.90 (0.83 to 0.98)	0.016	1.16 (1.06 to 1.27)	0.001
8.7–10.7	0.83 (0.77 to 0.88)	<0.007	0.87 (0.81 to 0.93)	<0.007
10.8–12.8	0.80 (0.76 to 0.84)	<0.007	0.95 (0.88 to 1.02)	0.190
12.9–14.9	0.80 (0.76 to 0.84)	<0.007	0.92 (0.87 to 0.97)	0.004
>14.9	0.77 (0.73 to 0.80)	<0.007	0.88 (0.83 to 0.93)	<0.007

IRR = incidence rate ratio.