Response to Afshar and Albrecht's (2017) Letter to the Editor.
We greatly appreciate Afshar et al.'s interest and comments on our published article entitled “Acute Alcohol Exposure and Risk of Mortality of Patients with Traumatic Brain Injury: A Systematic Review and Meta-analysis”. They noted that methodological issues in our paper should be considered to provide an unbiased conclusion. Considering the limitations of observational studies, we agree with some of Afshar et al.'s suggestions in their letter to the editor. However, we have our own views on the limitations mentioned in the letter. 
 
The authors argue that a selection bias exists when using data from trauma centres. They imply that blood alcohol concentration (BAC) is not systematically assessed and that missing values are not missing at random. 
 
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