Systematic reviews are summaries of the information that is available on one topic. The most common way to find information for a systematic review is to search electronic literature databases. To increase the chances of finding important information, researchers can also search the tables of contents of journals, and they can contact experts or organizations for more information on the topic of the review. Another way to find more information is to check through the reference lists of relevant studies to see if these references include reports of other studies that might be eligible for the review. It is important to determine whether or not checking reference lists is a good use of time and resources when conducting systematic reviews.
We found 12 studies that explored whether or not checking reference lists was useful for systematic reviews. These studies reported a range of results, from identifying only a few additional studies (2.5%: 2 of 79 included studies) to identifying many additional studies (42.7%: 111 of 260 included studies) through checking reference lists. Unfortunately, none of the studies looked at how much time or money were spent on the process of checking reference lists, and it was suggested this would be almost impossible to estimate.
Unfortunately our findings are based on weak information. The data do suggest that in situations where researchers may have difficulty locating information, checking through the reference lists may be an important way to reduce the risk of missing relevant information.