Case-control studies or cohort studies with a nested case-control group that allowed mortality rates of head injury patients on warfarin to be compared with those not on warfarin were eligible for inclusion. Studies of trauma patients on anticoagulants were included if they provided data to enable consideration of a subset analysis of mortality rates in the head injury group. Studies that examined the effect of antiplatelet agents were excluded. Also excluded were studies of patients with minor head injury (Glasgow Coma Scale 15) and those in which the subgroup of patients on warfarin could not be distinguished from those who took other agents (such as aspirin or clopidogrel). No lower sample size limits were applied.
Studies included patients with various types of head injury, some requiring confirmation on computed tomography and others applying certain ICD-9 (International Classification of Diseases 9) codes as inclusion criteria. Most studies did not report the injury composition of included patients. Mean age of patients was 70.2 to 81.9 years in the warfarin group and 54 to 81.7 years in the non-warfarin group. Mean ratings on the Glasgow Coma Scale and injury severity scores were similar between groups (range 11 to 14.13 and 10.4 to 24.9). The mean international normalised ratio (INR) ranged from 2.3 to 3.3. Where reported, INR was corrected using fresh frozen plasma (FFR) with or without vitamin K.
The search was conducted by one author. Full papers were reviewed by another author.