A “search hedge” is a library term that describes one of two things:

Search Filters

Search filters are found within a database and work by assisting the user with locating articles for a specific type of question by filling out a form/selecting a pre-set filter.

PubMed Clinical Queries

PubMed Clinical Queries are a built-in search hedge found in PubMed, that assists users in locating clinical studies to answer clinical questions. Users simply enter their search terms and answer several questions (such as whether the question is related to diagnosis, therapy, prognosis, or etiology), and from there PubMed adds a pre-set hedge that is designed specifically for the answers provided.

The search hedge itself is “hidden” from the search strategy seen by the user, however the complete hedge can be viewed in the Clinical Queries filter details.

Embase Search tools

When using Embase (on the Elsevier platform) there are several built-in search tools available to help quickly filter results when searching on specific topics, including: PICO, PV Wizard, and Medical Device.

PICO

The PICO search tool assists in doing evidence-based practice by providing separate sections to enter each component of the PICO framework (population, intervention, comparison, outcome) as well as study design, to quickly identify clinical studies to answer the clinical question being addressed.

PV Wizard

The PV Wizard (PV stands for pharmacovigilance) allows the user to locate articles that address drug monitoring and adverse events using specific drug names (including trade, generic, and alternate names), with buttons to limit to things like adverse reactions, drug interactions, drug combinations, as well as special situations (pregnancy, breastfeeding, pediatric, geriatric, organ failure, etc.).

Medical Device

The Medical Device search allows users to quickly locate clinical and pre-clinical studies on general and medical devices, including manufacturers information and adverse events. This search hedge was developed and validated by industry representatives to ensure that it aligns with best practices for medical device monitoring.

Embase Quick Limits

Embase has several “quick limits” which are essentially search filters that can be added using a single click. These limits can be added by either checking off a box or by adding a specific field code to your search strategy.

• Humans: Either the Humans quick limit button or the field code [humans]/lim
• Animals: Either the Animal quick limit button or the field code [animals]/lim
• EBM: Quick limit button for Cochrane Reviews, Controlled Trials and RCTs

Search Hedges

Search hedges are comprehensive search strategies for a specific database on topics or concepts that have been devised by librarians or information professionals. These hedges are published and available for anyone to use, and many are also validated. While hedges can be used on their own, as ready-made searches on various topics, they are most often added on to the user’s search strategy to limit or narrow the results.

Most search hedges are designed for things like specific populations, study types, diseases or conditions, or outcome measures. Typically a search hedge can simply be copied and pasted into the database, and then using the Boolean operator AND, added to a search already created.

Embase Study Type Hedges

The Embase Study Type Hedges are standardized search strategies for common and frequently used concepts that can used along with a search query. These search strategy hedges can be copied and pasted into the search box in Embase and then added to an already designed search using the Boolean operator AND.

These hedges are to be used to focus on locating specific types of clinical or experimental studies, and each hedge has an option for either sensitivity (comprehensive) and specificity (focused) based results.

There are several types of hedges available on Embase.com.

• General Study Types: Therapy, Diagnosis, Prognosis, Etiology, Economics, etc
• Hedges by Topic: Diabetes, Real-World Data, Cost Effectiveness, DEI
• Animal Breed Hedges: Species-specific hedges for most animals used in research and agriculture

Locating Search Hedges

Since search hedges are published search strategies on specific topics, they can be found in a variety of places online. Some, such as the Study Type Hedges in Embase and the Study Type Filters in PubMed, are available from the database itself. Others can be found on various library websites, published literature, and in special search hedge repositories (though these may not be validated).

It’s common to find search hedges in systematic review resources, since systematic reviews require comprehensive search strategies, and search hedges can provide just that.

A validated search hedge is the “gold-standard” and has been independently tested and verified, so if there is a validated hedge available for the topic you are looking for, that is your best option.

Search Hedge Sources

• Canada’s Drug Agency (formerly Canadian Agency for Drugs and Technologies in Health [CADTH]): Search Filter Database
• McMaster Health Information Research Unit (HIRU): Hedges Project
• InterTASC Information Specialists Sub-Group (ISSG): Search Filter Resource
• University of Alberta: Health Sciences Search Filters
• Library of Search Strategy Resources (LSSR): Collections
• CABI Digital Library: SearchRxiv

Suggested Reading

What is the difference between a filter and a hedge?. J Eur Assoc Health Info Libr [Internet]. 2016 Apr. 1 [cited 2025 May 6];12(1). Available from: https://ojs.eahil.eu/JEAHIL/article/view/95

At the end of each year, the National Library of Medicine (NLM) produces their annual updates to PubMed’s MeSH (Medical Subject Headings). These changes are made at every level of the MeSH infrastructure, including descriptors (headings or terms), qualifiers (subheadings), and supplementary concepts, and are made in response to changes in scientific discovery, taxonomy, ethical considerations, and published literature. The National Library of Medicine describes the necessity of these changes as this: “In biomedicine and related areas, new concepts are constantly emerging, old concepts are in a state of flux and terminology and usage are modified accordingly. To accommodate these changes, descriptors must be added to, changed or deleted from MeSH with adjustments in the related hierarchies, the Tree Structures.”

Types of MeSH Changes

• Added Terms — brand new terms added, either as MeSH headings or Supplementary Concepts that currently do not warrant a full heading
• Modified Terms — MeSH concepts that were changed (either name or hierarchical location), also referred to the the “Preferred Term“
• Replaced Terms — Descriptors or Supplementary concept terms are replaced by another term; this can include Supplementary Concepts upgraded to Descriptors as well as merged terms
• Merged Terms — Multiple Descriptor or Supplementary concept terms combined under a single concept term
• Combined Terms — Descriptor and Qualifier (subheading) combination made into a new separate concept
• Deleted Terms — Descriptor or Supplementary concept terms removed, due to either being combined, upgraded, or renamed

What’s New in 2025

Artificial Intelligence

The 2025 Annual MeSH Update includes a variety of important and much-needed changes. One of the biggest and most needed expansions in the 2025 update is to the Artificial Intelligence concept, including dozens of new MeSH Descriptors found within the broader concept, including:

• Autonomous Robots
• Generative Artificial Intelligence
• Intelligent Systems
• Machine Pattern Analysis
• Machine Prediction Methods
• Prediction Algorithms

Publication types

Several changes were made to publication types for MeSH 2025, including two new publication types:

• Network Meta-Analysis
• Scoping Review

Note: The NLM has made an exception to their general rule of not retroactively indexing; so just as they did in 2019 when “Systematic Reviews” became a separate publication type, citations will be retroactively updated to reflect these two new publication types.

The Network Meta-Analysis publication type was previously a Descriptor (MeSH Heading); thus for existing citations, the Descriptor term (“Network Meta-Analysis”[MeSH]) will be replaced with either the “Network Meta-Analysis”[Publication Type] OR “Network Meta-Analysis as Topic”[Mesh] as appropriate. This is an important change, as it extends the scope of indexing the publication type back to the introduction of the original term in 2017.

The “Scoping Review”[Publication Type] will replace either the “Review”[Publication Type] or “Systematic Review”[Publication Type] on appropriate citations extending back to 2020, the first year this term appears in MEDLINE. Additionally, “Scoping Review as Topic”[Mesh] has been expanded from the “Review as a Topic”[Mesh] term.

Additionally, NLM will discontinue indexing following Publication Type terms:

• Autobiography
• Bibliography
• NIH Consensus Development Conference
• Dictionary
• Directory
• Interactive Tutorial
• Legal Case
• Legislation
• Periodical Index
• Portrait
• Technical Report

Note: As with previously discontinued Publication Types, which include “Government Publication,” “Newspaper Article,” “Overall,” and “Scientific Integrity Review,” these Publication Types will continue to exist in MeSH, appear on existing citations, and be searchable in PubMed. However, they will no longer be applied to new citations.

How Does this Impact Searching?

Since there are so many changes to MeSH terms and structure, if you save search strategies or search alerts, or want to rerun a search that was previously conducted (such as from a systematic review), these changes may impact if and how your search strategy functions. Below are some steps to take to ensure that your search strategy is not only viable but also the best reflection of the current database.

1. Check search viability — Run your search in PubMed and go to Advanced Search and check if there are issues being highlighted in the Details section. Terms that were removed or modified (name changed, upgraded, merged, etc.) will likely be in red. If your search is suddenly retrieving no results, this also could be the cause.
2. Identify relevant new terms — Refer to the New MeSH Descriptors for 2025 list to see if there are any relevant terms that were added for 2025 that may make your search strategy more robust or specific.
3. Identify replaced terms — Refer to the MeSH 2025 – Replace Report to identify any terms that were replaced by another term, upgraded to Descriptors, or consolidated with another term.
4. Review publication types — Refer to the Annual MeSH Processing for 2025 NLM Bulletin for changes to publication types

If you have searches saved in your My NCBI account and/or you are getting PubMed e-mail alerts, or if you need to update your Systematic Review based on your previous search strategy, you may want to consult a Research Informationist to ensure your saved searches are not affected by the annual changes in the MeSH terminology. Don’t hesitate to ASK US!

Important Note from NLM Regarding Reindexing

Typically, the NLM does not retroactively re-index MEDLINE citations with new MeSH heading concepts. Therefore, searching PubMed for a new MeSH term tagged with [mh] or [majr] effectively limits retrieval to citations indexed after the term was introduced. Searchers may consult the MeSH database to see the previous indexing terms most likely used for a particular concept before the new MeSH heading was introduced. For terms without previous indexing information, consider the next broader term(s) in the MeSH hierarchy. or more searching guidance, see the on-demand class MeSH Changes and PubMed Searching.