Fig. 2

Flow chart of data handling procedures describing the process through which patients are enrolled in the study and data is de-identified. 1 Research assistants review the emergency department (ED) visit logs, identify injured drivers, and determine whether blood work is ordered. 2 Research assistants maintain a temporary link file between patient identifiers and study ID. 3 Chart data linked to study ID is entered into REDCap database. Only basic information is recorded for excluded drivers. The research assistant also provides the laboratory with a list of eligible drivers so that excess blood can be relabelled with study ID and frozen pending shipping to coordinating site. 4 Every 3 months, blood sample are shipped to the coordinating site. At the coordinating centre, blood samples are relabelled with a Toxicology ID replacing the study ID number. A permanent link between study ID number and toxicology ID is maintained at the coordinating site. 5 Once a month, the study coordinator reviews data (in REDCap) for completeness and to conduct error checks. 6 Once data is verified and downloaded, the study coordinator instructs the site research assistants to destroy the temporary link file. After this point there is no linkage between excess blood samples and personal identifiers. 7 The site coordinator sends blood to the toxicology lab for analysis. After blood is analyzed excess samples are destroyed. 8 Toxicology results are sent to study coordinator and linked the to study ID number. The research coordinator merges the results with chart review data. 9 Chart data and toxicology results are stored locally on a password protect computer in a locked office