Machine learning reduced workload with minimal risk of missing studies: development and evaluation of a randomized controlled trial classifier for Cochrane Reviews

J Clin Epidemiol. 2021 May;133:140-151. doi: 10.1016/j.jclinepi.2020.11.003. Epub 2020 Nov 7.


Objectives: This study developed, calibrated, and evaluated a machine learning classifier designed to reduce study identification workload in Cochrane for producing systematic reviews.

Methods: A machine learning classifier for retrieving randomized controlled trials (RCTs) was developed (the "Cochrane RCT Classifier"), with the algorithm trained using a data set of title-abstract records from Embase, manually labeled by the Cochrane Crowd. The classifier was then calibrated using a further data set of similar records manually labeled by the Clinical Hedges team, aiming for 99% recall. Finally, the recall of the calibrated classifier was evaluated using records of RCTs included in Cochrane Reviews that had abstracts of sufficient length to allow machine classification.

Results: The Cochrane RCT Classifier was trained using 280,620 records (20,454 of which reported RCTs). A classification threshold was set using 49,025 calibration records (1,587 of which reported RCTs), and our bootstrap validation found the classifier had recall of 0.99 (95% confidence interval 0.98-0.99) and precision of 0.08 (95% confidence interval 0.06-0.12) in this data set. The final, calibrated RCT classifier correctly retrieved 43,783 (99.5%) of 44,007 RCTs included in Cochrane Reviews but missed 224 (0.5%). Older records were more likely to be missed than those more recently published.

Conclusions: The Cochrane RCT Classifier can reduce manual study identification workload for Cochrane Reviews, with a very low and acceptable risk of missing eligible RCTs. This classifier now forms part of the Evidence Pipeline, an integrated workflow deployed within Cochrane to help improve the efficiency of the study identification processes that support systematic review production.

Keywords: Automation; Cochrane Library; Crowdsourcing; Information retrieval; Machine learning; Methods/methodology; Randomized controlled trials; Searching; Study classifiers; Systematic reviews.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms*
  • Databases, Bibliographic / standards
  • Databases, Bibliographic / statistics & numerical data
  • Humans
  • Information Storage and Retrieval / methods*
  • Information Storage and Retrieval / standards*
  • Information Storage and Retrieval / statistics & numerical data
  • Machine Learning*
  • Randomized Controlled Trials as Topic / classification*
  • Randomized Controlled Trials as Topic / methods
  • Randomized Controlled Trials as Topic / standards*
  • Randomized Controlled Trials as Topic / statistics & numerical data
  • Systematic Reviews as Topic / methods
  • Systematic Reviews as Topic / standards*
  • Workload / statistics & numerical data*