Understanding search failures in consumer health information systems.

We examined queries that led to search failures on two National Library of Medicine Web-based consumer health sites, ClincialTrials.gov and MEDLINEplus. The purpose of the study was to analyze and categorize queries resulting that led to no results with the ultimate goal of developing interventions to assist users in recovering from those failures. We first analyzed over 2,700 queries, iteratively developing a coding scheme. We subsequently applied the codes to an additional set of 2,000 queries. We found that most of the queries were in scope, relevant to the system being searched, and did not exhibit so-called consumer language. As the final step, we developed a taxonomy based on whether the search failures were due primarily to content issues, to problems in query formulation, or to limitations of the search system. The results reported here have informed the further development of our own systems, and they may be helpful to others as they seek to improve consumer access to health information.