Systematic review identifies six metrics and one method for assessing literature search effectiveness but no consensus on appropriate use.

Objectives: To identify the metrics or methods used by researchers to determine the effectiveness of literature searching where supplementary search methods are compared to bibliographic database searching. We also aimed to determine which metrics or methods are summative or formative and how researchers defined effectiveness in their studies.

Study Design And Setting: Systematic review. We searched MEDLINE and Embase to identify published studies evaluating literature search effectiveness in health or allied topics.

Results: Fifty studies met full-text inclusion criteria. Six metrics (sensitivity, specificity, precision, accuracy, number needed to read, and yield) and one method (capture recapture) were identified.

Conclusion: Studies evaluating effectiveness need to identify clearly the threshold at which they will define effectiveness and how the evaluation they report relates to this threshold. Studies that attempt to investigate literature search effectiveness should be informed by the reporting of confidence intervals, which aids interpretation of uncertainty around the result, and the search methods used to derive effectiveness estimates should be clearly reported and validated in studies.