Table 2

Setting, locations, relevant dates and other study characteristics: multisite review of ICD-10-CM codes for intracranial injury and skull fracture treated in EDs

Study sites	One shock trauma, One ED in referral centres	Two EDs in university system	EDs in level I, II, III trauma hospitals	EDs in all acute care hospitals
State of study site	Maryland	Kentucky	Colorado	Massachusetts
Setting: type of hospital	Large academic hospitals*	Acute care hospitals	Acute care hospitals in 11 urban counties†	All acute care hospitals in the state
Number of hospital EDs in the study	2	2	29	73
Percentage of state population covered by hospitals (catchment area)	15	38	83	100
Dates of the ED visits in the billing dataset	January 2016- December 2018	January 2016- June 2018	January 2017-December 2017	October 2015-September 2016
Number of diagnosis fields in the ED billing dataset	30	25	30	34
Type of medical record reviewer	18 clinical researchers	2 trauma nurses	1 professional MR coder	3 professional MR coders
Access to electronic medical record	Yes	Yes	ED report and EMS transport‡	ED report and EMS transport‡

*In Maryland, one of the two sites was a neurotrauma referral centre, not an ED, and its trauma registry was used for sampling.
†The Colorado team selected the 29 acute care hospitals that had a trauma designation of level I, II or III, and located in Colorado’s 11 most populous counties. These 29 hospitals had 77% of all ED visits for intracranial injury and 81% of all ED visits for skull fractures (without an intracranial injury) in the state during the study time period.
‡Additional medical documents requested in Colorado: face sheet, radiology reports, toxicology reports. Massachusetts: face sheet, radiology reports, lab work/lab notes, triage notes, history and physical.
ED, emergency department; EMS, emergency medical services; ICD-10-CM, International Classification of Diseases, Tenth Revision, Clinical Modification; MR, medical record.