Ovid Tools & Resources Portal

In recent publications, Ovid MEDLINE results are recognized as being most consistent with PubMed’s. Yet there are differences in search behavior and indexing that can lead to a common misconception that Ovid is sometimes underreporting, when comparing searches between Ovid MEDLINE and PubMed. This document addresses those concerns, and explains how to best compare the two platforms.

For information about the Ovid MEDLINE ALL segment, please see this article:

https://wkhealth.force.com/ovidsupport/s/article/MEDLINE-ALL-FAQ

Phrase searching:

Multi-word search terms are searched as phrases in Ovid. There is no need to place quotation marks around these phrases unless the phrase contains operators for Ovid (e.g. “and”, “or”, “not”, “use” etc.) or special characters (e.g. à, ç, è, é, ê etc.).

In PubMed Advanced Search you have to place quotes around the multiword terms to do the same. But in that case, wildcards cannot be used and some phrases cannot be searched in PubMed, even though they are present in one or more records.

Using the PubMed entry page search box, many but not all phrases are recognized and searched using its MeSH Translation Table. Phrases in PubMed are not recognized when hyphens or quotation marks, a Medical Subject Heading (MeSH), or truncation are used.

In addition, Ovid has an adjacency operator:

ADJn is a positional operator. It is very useful to search for specific phrasing, complex or expert searching. When this is used in between 2 search terms, you will search for both terms, in any order, with up to (n-1) words in between.

The number of “n” can be from 1 to 99, but in most searches a number from 1 to 10 will be fine.

You can test different numbers for n (for example 3, 4, 5) and look at the extra records of these subsequent searches. Decide from these results which “n” you prefer.

Be aware that ADJn is important in free text searching!

For example, the search (kidney adj3 diseases).ti,ab. retrieves records that contain the words kidney and diseases with up to 2 words in between, in any order, in titles and abstracts.

The ADJn operator is more specific than the AND operator (kidney AND diseases), but less specific than a phrase (kidney diseases). With kidney ADJ3 diseases you will retrieve records containing kidney diseases, kidney and liver diseases, diseases of the kidney.

The ADJn can also be used with truncated terms, for example (kidney* ADJn disease*).ti,ab.

In November 2022 PubMed announced that they would provide a limited adjacency search capability. PubMed adjacency currently only works in the title and abstract fields and truncation is not available.

When using the ADJn operator as part of a fielded search, it is best to combine it with word-indexed fields. To learn what fields are word-indexed, refer to the field guide of the database that you are searching.

In PubMed right-hand (= end) truncation, for example gene*, searches all terms that begin with gene. This generates a large variety of search terms, though you may not be interested in all of them: gene, general, generation, genes, genetics, Geneva, etc. PubMed now supports expanded use of the asterisk (*) wildcard in the middle of a term or phrase. A PubMed wildcard (*) substitutes 0 or more characters. Terms must have at least 4 characters before the first wildcard in PubMed.

Ovid offers additional truncation options. Limited right-hand truncation is supported, as well as limited wildcards within a word or at the end of a word. On Ovid, only one character is needed before the first truncation or wildcard.

These Ovid values provide greater precision in searches:

In PubMed Advanced Search you can choose between an explode or a non-explode (for MeSH Subject Headings that have Narrower Terms).

When you want to search with a MeSH Subject Heading and only some of its Narrower Terms, PubMed offers separate search options to choose subject headings using a PubMed MeSH tool, or NLM’s MeSH on Demand or the MeSH Browser.

In Ovid it is easy to select only some of the narrower subject heading in MeSH for your search by using the MeSH Tool tab in your search window. When you see a subdivided MeSH Subject Heading in the Thesaurus, you may tick this Subject Heading (without ticking its explode) and also the individual narrower Subject Headings you are interested in.

When you are interested in the Subject Heading, 'Light', and in 3 of its narrower Subject headings, Infrared Rays, Sunlight, Ultraviolet Rays, but not in Color, Darkness, Glare, Incandescence, Luminescence, Fluorescence, Photons, you tick Light (without Explode), Infrared Rays, Sunlight, Ultraviolet Rays.

In PubMed linked subheadings that have narrower subheadings, automatically are exploded so that the search includes the more specific subheadings beneath the broader subheading.

In PubMed you can turn off the automatic EXPLODE for subheadings, but need to know the PubMed syntax to use. If you do not do that the following occurs:

"Aspirin/adverse effects"[Mesh] gives the same number of records as “Aspirin/adverse effects"[Mesh] OR "Aspirin/poisoning"[Mesh] OR "Aspirin/toxicity"[Mesh].

In Ovid MEDLINE^® it is fast and easy to search for Aspirin as a Subject Heading with only the single linked subheading adverse effects, for example:

Aspirin/ae, po, to [Adverse Effects, Poisoning, Toxicity] gives (many) more records than Aspirin/ae [Adverse Effects]

Be aware that when you are interested in ALL adverse effects of aspirin, that is in all kinds of doses, you must include the subheadings poisoning and toxicity in addition to adverse effects.

Use the OR operator to combine results sets into a single set inclusive of all records from the results sets indicated. For example, the search 1 or 2 or 3 combines results from the first, second, and third sets into a single set.

You can also do a combination search like OR/2-20.

There can even be “gaps” in long ranges, for example: OR/4-6,8-20

In PubMed the OR operator can be used in the Advanced Search Builder to combine disparate set numbers with syntax, though there is nothing similar to the Ovid OR/ feature.

Date Range searching in bibliographic databases is an important feature, when the researcher needs to detect new records added to the database. When repeating a search strategy associated with an earlier literature review, you want to understand which records were added to the databaser copared to when that review was done. This is a very important aspect of any systematic review project or exploration prior to a review.

For detailed information how to perform date-range searching in Ovid MEDLINE please consult: https://wkhealth.force.com/ovidsupport/s/article/Limit-by-date-range-in-Ovid

Options with Set Numbers:

When you have made an Ovid/MEDLINE^® search (concerning several free text terms in the titles, abstracts and author keywords), and later on you want to change this to a search in titles, this can be done very easily.

This is also true when you want to change an explosion with subheadings to the Focused form.

• If line 1 of search strategy = (cancer* or neoplas* or tumor* or tumour*).ti,ab,kf.
• 1.ti will return (cancer* or neoplas* or tumor* or tumour*).ti.
• If line 3 = exp Neoplasms/ec[Economics]
• *3 will return exp *Neoplasms/ec

In PubMed some but not all of these changes are possible in the Advanced Search Builder. Terms that are combined by OR all need a separate field identification in PubMed.

You need to use PubMed syntax to change an explosion with subheadings to the Focused form: neoplasms/ec to either neoplasms/ec[majr] or neoplasms/ec[majr:noexp]

Adding, editing multiple subheadings for a subject heading:

• In PubMed, only one subheading can be attached to a subject heading at a time. Thus you need to repeat the subject heading for each subheading and OR them together in PubMed. On Ovid MEDLINE^®, you can string multiple subheadings onto one subject heading, and edit them on one line: exp Neoplasms/ec, ge, sn to: exp Neoplasms/ec, dt, sn

Searching only in the ABSTRACT field:

• PubMed searches title and abstract together and you cannot edit a search to search only in the abstract field. Ovid MEDLINE^® provides you the ability to search ONLY in the abstract field: Neoplasms.ab.

You can search several third party databases with the same Ovid “language” when subscribing to multiple databases from the more than 100 available on the Ovid platform (e.g. Embase, PsycINFO, etc.)

On PubMed you can search 50+ databases developed by or in partnership with the U.S. National Institutes of Health, NCBI, using PubMed syntax.

In PubMed, Search History can be modified however, you will not get a warning message if a deleted set negatively impacts other sets. There is no feature to automatically renumber sets when modifications are made to sets in PubMed Search History. PubMed, Recent Activity however provides you a history of searches for the last 6 months (when signed into your NCBI account).

In Ovid MEDLINE^®, when removing one or more sets from the Search History

• a warning is given when more sets will be affected
• sets are “renumbered”

So in Ovid you always have a neat Search History.

Searches on Ovid can be edited and annotated for the current session as well as after saving the strategy.

PubMed searches can be edited as previously described, or edited in a saved search. However, PubMed searches cannot be annotated in the way that Ovid MEDLINE^® searches are.

Searches on Ovid can be edited and annotated for the current session as well as after saving the strategy.

LinkOut Ovid MEDLINE comes with the free of charges Link@Ovid module that allows easy configuration of your Library holdings and activate LinkOut to all Full Text subscription. The export/impor utilitilitay facilitates batch enabling of large numbers of titles, as if required Link@Ovid allows to integrate with library catalogues, document delivery services or ILL

Integration with Ovid Full Text is automatic for existing customers of Ovid MEDLINE^®, including the EBMR databases (Cochrane etc). On PubMed the customer has to configure LinkOut (see above)

In Ovid MEDLINE^®, the frequency operator (FREQ) lets you specify a threshold of occurrence of a term in the records in your search. Records containing your search term are retrieved ONLY if that term occurs at least the number of times you have specified. Generally, records that have many instances of your search term are more relevant and it can be very useful for searching common words in text fields like abstract or full text linked to the Ovid MEDLINE^® record.

Example: blood.ab/freq=5. PubMed does not offer this feature.

When using FREQ as part of a fielded search, it's best to combine it with word-indexed fields. To learn which fields are word-indexed, refer to the field guide of the database that you are searching.

Export options on Ovid MEDLINE^® include several report format options including Microsoft Word or Excel, Adobe PDF and XML. These save time manipulating and converting results into other formats post-search. PubMed offers text or CSV files, which may require post-processing into other formats. Ovid MEDLINE^® offers the choice of fields to export in the report. You can choose any combination of fields or all fields for the export of your results set. PubMed has a no options for field customization in the export.

Ovid MEDLINE^® offers many options for customizing the display format of the MEDLINE^® search results in the search results window and this can greatly assist and speed the online reviewing of records for a particular research need. For example you can customize the results to show only the title and institutional affiliation, or subject headings, or name or number of substance. PubMed offers standard formats: Summary, Abstract, MEDLINE^®, XML, PMID list.

Ovid has integrated the Clinical Queries developed by McMaster University into the limit option on Ovid MEDLINE^®. On PubMed, the Clinical Queries are available to search in a separate search interface and not integrated into the PubMed search interface. On Ovid MEDLINE^® these Clinical Queries are available with one click in the limits and can assist in quickly narrowing clinical results. They include the following:

• Reviews – maximizes sensitivity
• Reviews – maximizes specificity
• Reviews – best balance of sensitivity and specificity
• Therapy - maximizes sensitivity
• Therapy – maximizes specificity
• Therapy – best balance of sensitivity and specificity
• Diagnosis– maximizes sensitivity
• Diagnosis – maximizes specificity
• Diagnosis – best balance of sensitivity and specificity
• Prognosis – maximizes sensitivity
• Prognosis – maximizes specificity
• Prognosis – best balance of sensitivity and specificity
• Causation-Etiology– maximizes sensitivity
• Causation-Etiology – maximizes specificity
• Causation-Etiology – best balance of sensitivity and specificity
• Economics – maximizes sensitivity
• Economics – maximizes specificity
• Economics – best balance of sensitivity and specificity
• Clinical Prediction Guides – maximizes sensitivity
• Clinical Prediction Guides – maximizes specificity
• Clinical Prediction Guides – best balance of sensitivity and specificity
• Qualitative – maximizes sensitivity
• Qualitative – maximizes specificity
• Qualitative – best balance of sensitivity and specificity
• Costs – maximizes sensitivity
• Costs – maximizes specificity
• Costs – best balance of sensitivity and specificity

You can use Special Ovid Filters to restrict retrieval to a pre-defined set of records, populated by a special Ovid search strategy for that topic. As the results sets for these filters are created with every database update, the results display quickly. Ovid filters are "AND" combined with the search line you are trying to limit, unless stated otherwise (e.g. humans only). Each of the search hedges below are based on publicly available filters that have been reviewed, translated and improved by Ovid expert searchers. While these filters aren't validated by Ovid, we provide the full transcript for each filter below and we have placed a reference for each filter where applicable. Full detail on the below listed filters can be found in the database guide for Ovid MEDLINE: (https://ospguides.ovid.com/OSPguides/medline.htm#limits. Ovid welcomes your suggestions to enhance the filters; to provide feedback and ideas for the Special Ovid Filters, please contact [email protected] .

• Adverse effects
• Adverse effects - focussed
• Children
• Children - focussed
• Elderly
• Elderly - focussed
• Humans only (removes records about animals)
• Pregnancy - wide
• Pregnancy - focussed