The challenge of high recall in biomedical systematic search

Clinical systematic reviews are based on expert, laborious search of well-annotated literature. Boolean search on bibliographic databases, such as MEDLINE, continues to be the preferred discovery method, but the size of these databases, now approaching 20 million records, makes it impossible to fully trust these searching methods. We are investigating the trade-offs between Boolean and ranked retrieval. Our findings show that although Boolean search has limitations, it is not obvious that ranking is superior, and illustrate that a single query cannot be used to resolve an information need. Our experiments show that a combination of less complicated Boolean queries and ranked retrieval outperforms either of them individually, leading to possible time savings over the current proces