Searching for the evidence: source, time and yield

Article type
Authors
Hayward S, Brunton G, Thomas H, Ciliska D
Abstract
Objective: This study was designed to determine the search yield by source and time of articles for a systematic overview.

Methods: Electronic databases (online, network and CD ROM databases), key journals and books by hand, and bibliographic references were searched using a defined search strategy, and key informants were contacted for relevant articles. Retrieved articles, relevance and quality assessment testing results were totalled by source. Time was tracked using tally sheets and included searching, retrieval, copying, travel, and recording time.

Results: Library document delivery time was 20 minutes per article, regardless of source. Electronic databases yielded a higher proportion of quality articles than other sources (1 article retrieved every 1.07 minutes of searching). Hand searching was the most time consuming source (1 article retrieved every 27.73 minutes of searching) and returned the highest proportion of poor quality articles. Many references found while hand searching were duplicates already retrieved from electronic database searching, yet some unduplicated articles were found.

Discussion: Searching by electronic database was the most comprehensive and efficient means of retrieving articles for further relevance testing. Most time on this source was spent defining a specific search question and refining the resulting search strategy. Other sources of retrieval were more time-consuming and often yielded articles already found by electronic searching but still provided articles which may have not otherwise been discovered. Hand searching is the most time intensive. To make searching more expedient, a hierarchy should be followed: searching electronic database sources first to retrieve the majority of possibly relevant articles; searching by hand and contacting key informants next to elicit specific and difficult to find relevant articles; and searching bibliographic listings to reveal further previously undiscovered articles. Findings to date indicate that the specificity of the research question and access to a variety of retrieval sources may influence the comprehensiveness of the retrieval.