Impact of a change of bronchodilator medications in a hospital drug formulary on intra- and out-of-hospital drug prescriptions: interrupted time series design with comparison group

Table 2 Interrupted time series segmented regression analysis with control group of inhaled corticosteroid and long-acting β2-agonist combinations (ICS-LABA)

	Pre-intervention trend		Post-intervention
	Pre-intervention trend		Immediate impact of the formulary change		Change in trend after the formulary change
	Coefficient	95% confidence interval	Coefficient	95% confidence interval	Coefficient	95% confidence interval
DDD/100 stays-day
Total ICS-LABA	− 0.464	− 2.117 to 1.188	3.344	− 10.312 to 17.002	0.317	− 1.359 to 1993
Formoterol/budesonide^a	0.012	− 1.438 to 1.464	15.830*	3835 to 27,825	− 0.200	− 1.672 to 1,272
Salmeterol/fluticasone^b	− 1.043	− 2.483 to 0.396	− 7.792*	− 15.113 to − 0.471	1.075	− 0.37 to 2.521
Inpatient expenditure per DDD
Total ICS-LABA	− 0.003	− 0.119 to − 0.113	− 0.953*	− 1.733 to − 0.174	0.009	− 0.108 to 0.127
DDD/TID
Total ICS-LABA	− 0.405	− 1.046 to 0.235	0.994	− 1.484 to 3.474	0.348	− 0.290 to 0.986
Formoterol/budesonide	0.066	− 0.102 to 0.235	− 0.015	− 0.820 to 0.790	− 0.068	− 0.238 to 0.101
Salmeterol/fluticasone	− 0.039	− 0.194 to 0.115	− 0.143	− 0.991 to 0.704	0.034	− 0.121 to 0.190
Formoterol/beclometasone	− 0.008	− 0.141 to 0.123	− 0.182	− 0.817 to 0.453	− 0.030	− 0.164 to 0.102
Formoterol/fluticasone	0.006	− 0.021 to 0.033	0.107	− 0.103 to 0.319	0.001	− 0.026 to 0.029
Vilanterol/fluticasone	0.008	− 0.01 to 0.027	− 0.023	− 0.154 to 0.107	− 0.017	− 0.037 to 0.002
Outpatient expenditure per DDD
Total ICS-LABA	− 0.405	− 1.046 to 0.235	0.994	− 1.484 to 3.474	0.348	− 0.290 to 0.986

^aThe only ICS-LABA that remained in the intervention hospital drug formulary after the intervention
^bAfter the intervention, this ICS-LABA was removed from the intervention hospital drug formulary (not at the control hospital)
*p < 0.05

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