Alcohol-related road traffic injury and Global Burden of Disease 2010.

1092 www.thelancet.com Vol 382 September 28, 2013 could be primarily due to diff erences in estimation methods. Compared with the methods based on direct observation that the four countries used, the GBD 2010 used a fi ve-step approach to estimate alcohol-related transport injury that was based on systematical review and synthesis of published and unpublished data because most countries lack highquality data such as the data for these four countries.The GBD method is more likely to be affected by some potential confounding factors than the direct method because few countries have data that can satisfy the requirement of the GBD fi ve-step method. For example, the aetiological eff ect size of alcohol use on transport injury may change over time and across countries, as other factors change. Country-specific and yearspecifi c eff ect sizes of alcohol use are unavailable. The GBD group has to use a systematic review to estimate the eff ect size and apply it to all countries and all years. Because of the large difference between GBD data and reported data from four countries with high-quality data, the GBD 2010 data should be used cautiously to support policy related to alcohol use. When possible, high-quality directly observed data should be given priority, and further studies are needed to explain the large diff erences observed.