Handling Article Dates
- MLM-AI always searches articles by the date they were added to the source database, ie. the "entry date" or "uploaded date".
- This approach avoids missed articles in periodic searches and returns more comprehensive results.
- MLM-AI can optionally search by publication dates in addition to the entry date. This option is on by default and can be configured in each Monitor.
The start and end dates of search results are important parameters when performing periodic MLM. When searching for articles there are two important dates to consider:
- The publication date of an article - the date the article was published, according to the source journal.
- The date an article becomes visible in a database - ie. the article's indexation date, or "first seen" date.
For example, an article may be published by a journal today, but it may be a few days or weeks before it enters the PubMed database and is visible on search results. Note however the publication date remains unchanged.
The diagram below illustrates the effects of this publication delay: a weekly search strategy that uses only the publication date could miss this article entirely.
To address this issue, MLM-AI always searches articles using the "entry date" at the source repository. This ensures that the article is retrieved if it became available at the source within the date range specified, even in cases where a publication is delayed.
In addition, MLM-AI provides monitoring configuration options to fine-tune the strategy:
- Include abstracts found by publication date - searches the same date range matching the publication date. This option is useful to maintain correspondence to existing manual search strategies.
- Discard publication dates older than 60 days - if the difference of an article first seen date and publication date is older than 60 days, results are discarded. This option is useful to avoid spurious results from "blanket" publication of journals going back many years.
Another reason to use article "first seen" date in searches is: publication dates can change over time in PubMed. This behavior is documented in PubMed help manual (excerpt shown below):
Most journals now publish articles online on a continuous basis, as soon as they are ready for publication (after peer review and editing, etc.) instead of, or in addition to, publishing collections of articles as an "issue" on a periodic basis.
When a journal deposits a citation for an "online first" article in PubMed, NLM appends the note "[Online ahead of print]" to the online publication date. The citation is updated, and the ahead of print notation removed, when the article is included in a journal issue. The lag between the "online first" and "issue" publication dates may be days, weeks, months, or more than a year.
This behavior is also reported by PubMed and searching by "entry date" brings more consistent results:
The time between an article’s publication and the citation’s availability in PubMed varies depending on when the publisher deposits the citation to PubMed. Because of this, searching with Create Date (the date a citation was created in PubMed) is often more comprehensive than Publication Date when checking PubMed on a regular basis for new citations.