Table 4

Interrupted time series model regression parameters: opioid overdose emergency department (ED) visit and hospitalisation rates per 100 000 population using three different ICD-9-CM indicator definitions

State	ICD-9-CM opioid overdose indicator definition†	ED visit regression parameters				Hospitalisation regression parameters
State	ICD-9-CM opioid overdose indicator definition†	Intercept‡	Time§	Transition¶	TimeAfter-Transition**	Intercept	Time	Transition	TimeAfter-Transition
Kentucky	Definition 1	0.54	0.07*	5.08*	−0.02	1.73*	0.00	1.56*	−0.03*
	Definition 2	0.61	0.07*	4.99*	−0.02	1.99*	0.00	1.37*	−0.03*
	Definition 3	1.04	0.07*	4.71*	−0.01	2.79*	0.00	0.63*	−0.02
Missouri	Definition 1	1.59*	0.02*	1.38*	0.05*	1.59*	0.00	1.36*	−0.02*
	Definition 2	1.66*	0.02*	1.33*	0.05*	1.76*	0.00	1.20*	−0.02*
	Definition 3	1.89*	0.02*	1.10*	0.05*	2.26*	0.00	0.67*	−0.02*
Montana	Definition 1	0.98*	0.00	0.68*	0.01	1.25*	0.00	0.74*	0.00
	Definition 2	1.03*	0.00	0.63*	0.01	1.29*	0.00	0.64*	0.00
	Definition 3	1.33*	0.00	0.45*	0.01	1.81*	0.00	0.29	0.00
New Mexico	Definition 1	3.40*	0.01*	1.20*	0.00	2.10*	−0.01*	1.44*	−0.02*
	Definition 2	3.49*	0.01*	0.84	0.02	2.30*	−0.01*	1.30*	−0.02*
	Definition 3	3.91*	0.02*	−0.06	0.01	2.95*	−0.01*	0.76*	−0.02
Nevada	Definition 1	2.27*	0.00	0.86*	0.01	1.87*	0.00	1.17*	−0.01
	Definition 2	2.57*	0.00	0.75*	0.01	2.09*	0.00	0.92*	0.00
	Definition 3	3.06*	0.00	0.27	0.01	2.69*	−0.01*	0.55*	0.01
Tennessee	Definition 1	1.27*	0.01*	1.48*	0.10*	1.60*	0.00*	1.34*	−0.02*
	Definition 2	1.46*	0.01*	1.35*	0.10*	1.91*	0.00*	1.10*	−0.02*
	Definition 3	1.97*	0.01*	0.97*	0.10*	2.48*	0.00	0.64*	−0.02*

Statistically significant results are marked with * (α=0.05).
†ICD-9-CM all-drug overdose indicator definitions (used prior to 1 October 2015): definition 1 searched the principal/first-listed diagnosis and first-listed valid external cause fields, definition 2 searched the principal/first-listed diagnosis and all external cause fields and definition 3 searched all available fields for the presence of an included code.
‡Intercept: estimated rate in January 2010.
§Time: average monthly change in rate (slope) from January 2010 to September 2015.
¶Transition: immediate level change observed in October 2015.
**TimeAfterTransition: change in slope after October 2015 compared with the pretransition slope.
ICD-9-CM, International Classification of Diseases, 9th Revision, Clinical Modification.