Limiting Searches To Time Spans (Date Range Searching) – Ovid MEDLINE

Background

The National Library of Medicine (NLM) in the USA is the provider of PubMed, a biomedical database comprising both MEDLINE and non-MEDLINE records. The database records are not an exact replica of the original article but rather an indexed and abstracted reflection of it. From the database provider’s perspective there are essentially three steps involved in converting documents, from their originally published format, into discoverable, searchable and retrievable database records. These are,

Step 1: The document is published in a source indexed by NLM for inclusion in PubMed/MEDLINE.
Step 2: The document’s record is created and enters NLM’s editorial and technical processing systems.
Step 3: The document’s record completes all the required processing for its designated status.

The processing of the document’s record is marked by a variety of time stamps, which as database fields, are indicated in the database record of the original document and hence are also searchable fields. Such instances include; the Year of Publication (YR), the Electronic Date of Publication (EP), the record’s Create Date (DT) as well as the Entry Date (ED). All these fields are phrase-indexed and are searchable using the format YYYYMMDD. An exception being the Year of Publication (YR) which has the format YYYY for both display and searching purposes.

This Focused Search look at ways in which searches can be limited to general or specific spans of time.

Limiting by a Range of Complete Years
The easiest way to limit a search to a range of complete years is to use the Year of Publication (YR) field. This field is marked and populated by the indexers as soon as the processing of the original document begins.  The database’s Limits function provides the option for the user to enter the wished for date range. Alternatively, set ranges, i.e. 3 Years, 5 years etc. can also be selected. All the records in PubMed and hence in Ovid MEDLINE have a year of publication. But note this is distinct from the dates connected to the document’s record being processed for inclusion in the database.

Limiting by Parts of Years
For searches across parts of years, down to months and even days, Ovid recommends using the Create Date (DT) field. This field marks the date when the document’s record was added to PubMed. As the date reflects the date on which the citation was added to the PubMed database, this is not the date of either the original document’s publication or even its electronic publication in the database. Also as a phrased-indexed field, the Create Date (DT) field lends itself well to truncation. So for example in the expression limit 1 to dt=202401*-202402* will yield results from all of January 2024 to all of February 2024.

Updating Search Strategies
Search strategies can be updated using the date range searching methods as described above. However, due to the inherent dynamism within the database’s records management, care must be taken when interpreting the results. An alternative method is to extract the records on, say day x and save them according to their unique identifiers (UI), either as a search in My Workspace or in a external document. Then later, on day y, run the same search and save these results similarly. Use the NOT operator to establish the difference between the results sets for day x and day y. This final result will indicate the number of records additionally found between day x and day y.

Practice Suggestions

1. How many records are there in Ovid MEDLINE whose publication date is in the 1800s?
2. The journal article entitled On the Cow-Pox was published in 1799. When was this record included in Ovid MEDLINE? When was the record last updated? How could you uniquely identify this record?
3. How could you use date range searching to illustrate the rapid rise of articles in Ovid MEDLINE that discuss the role of ChatGPT in health care?

 

Search Stategy

Copy Strategy Launch Search

Reviewers

Primary: Michael Fanning

Secondary: Charlotte Viken

Review Date: 2024-10-30

Expiry Date: 2025-10-30

Original search produced by:

Ovid Training Team

References:

Ovid / Knowledge Community
How can I limit search results by a date range in Ovid?

OvidGO! / Skills Videos
What are Boolean Operators?
What is an adjacency operator?
What are wildcards?
Truncation of keywords
Phrase searching on Ovid
Subject heading searching

Citation:

OvidGO! Portal. Focused Searches: Limiting Searches To Time Spans (Date Range Searching) – Ovid MEDLINE [Internet]. London (UK): Ovid Training Team (Editors); 2024 [updated 25 October 2024; cited 30 October 2024]. Available from: https://tools.ovid.com/ovidgo/searches/view.php?id=64