Objective: Hypothetically, content in MEDLINE records is consistent across multiple platforms. Though platforms have different interfaces and requirements for query syntax, results should be similar when the syntax is controlled for across the platforms. The authors investigated how search result counts varied when searching records among five MEDLINE platforms.

Methods: We created 29 sets of search queries targeting various metadata fields and operators. Within search sets, we adapted 5 distinct, compatible queries to search 5 MEDLINE platforms (PubMed, ProQuest, EBSCOhost, Web of Science, and Ovid), totaling 145 final queries. The 5 queries were designed to be logically and semantically equivalent and were modified only to match platform syntax requirements. We analyzed the result counts and compared PubMed’s MEDLINE result counts to result counts from the other platforms. We identified outliers by measuring the result count deviations using modified z-scores centered around PubMed’s MEDLINE results.

Results: Web of Science and ProQuest searches were the most likely to deviate from the equivalent PubMed searches. EBSCOhost and Ovid were less likely to deviate from PubMed searches. Ovid’s results were the most consistent with PubMed’s but appeared to apply an indexing algorithm that resulted in lower retrieval sets among equivalent searches in PubMed. Web of Science exhibited problems with exploding or not exploding Medical Subject Headings (MeSH) terms.

Conclusion: Platform enhancements among interfaces affect record retrieval and challenge the expectation that MEDLINE platforms should, by default, be treated as MEDLINE. Substantial inconsistencies in search result counts, as demonstrated here, should raise concerns about the impact of platform-specific influences on search results.

Document Type


Publication Date


Notes/Citation Information

Published in Journal of the Medical Library Association, v. 107, no. 3, p. 364-373.

Copyright © 2019 Christopher Sean Burns, Robert M. Shapiro II, Tyler Nix, Jeffrey T. Huber

This work is licensed under a Creative Commons Attribution 4.0 International License.

Digital Object Identifier (DOI)


Funding Information

The first author received support for this work with the 2018 Summer Faculty Research Fellowship Program of the College of Communication and Information at the University of Kentucky.

622-5334-3-SP.xlsx (343 kB)
Appendix A

622-5335-3-SP.pdf (78 kB)
Appendix B

622-5336-3-SP.pdf (97 kB)
Appendix C

622-5337-3-SP.pdf (57 kB)
Appendix D