Table 2.

Output from a multivariate segmented logistic regression with generalized estimation equations methods^* to predict the odds of receiving a head CT.

Variable	OR	95% CI
Baseline monthly trend preimplementation	1.00	0.99	1.00
Change from the last preintervention month to the first postintervention month	0.94	0.86	1.04
Change in monthly trend postimplementation	0.98	0.96	0.99
Age	1.02	1.02	1.02
Women	0.97	0.93	1.02
Race (reference=white)
Asian	1.28	1.17	1.39
Black	0.89	0.82	0.97
Hispanic	1.14	1.08	1.20
Other	1.01	0.83	1.23
High school education	1.00	0.92	1.10
Poverty	0.98	0.91	1.06
Marital status (reference=nonpartnered)
Partnered	0.93	0.89	0.97
Other/unknown	0.76	0.63	0.90
Elixhauser	1.05	1.03	1.07
Vomiting	0.99	0.89	1.09
Anticoagulants	1.19	1.11	1.26
GCS score <15	1.82	1.70	1.95
Medical center no. (reference=ED 13)
1	0.50	0.44	0.57
2	0.53	0.47	0.60
3	0.55	0.49	0.61
4	0.52	0.46	0.59
5	0.58	0.51	0.66
6	0.73	0.65	0.83
7	0.69	0.61	0.78
8	0.72	0.63	0.81
9	0.82	0.74	0.91
10	0.76	0.67	0.87
11	0.76	0.67	0.87
12	0.77	0.70	0.86
Emergency medicine residency	1.63	1.55	1.71
Years practicing (reference<3)
3–10	0.96	0.90	1.02
11–20	0.86	0.80	0.92
>20	0.79	0.73	0.85
Physician completed education of the Canadian CT Head Rule	1.06	0.94	1.19
Arrived by ambulance	1.06	1.01	1.11
Alcohol intoxication	3.64	3.05	4.35

^*Physician treated as a repeated measure to account for correlation between encounters from the same provider.