For quite long I had assumed that since PubMed Central (PMC for short) was included in PubMed, one did not have to search the PMC database – https://www.ncbi.nlm.nih.gov/pmc/ – separately.
PMC is an “archive” of free biomedical and life sciences journal articles. Journal articles are added and archived in PMC from three sources
- Journal publishers / Publishing societies
- Author manuscripts deposited by authors – as mandated by funders
- Digitization projects – where NLM has collaborated with publishers to archive historical literature – scanning articles and preserving them
From June 2020, PMC has also started including preprints that report NIH funded results
So in terms of the “database records”, PubMed comprises citations and abstracts only, whereas PMC comprises full text articles. Both PMC and PubMed have started including preprints since 2020. PMC has an author manuscript collection where an article could be from a journal that may not be otherwise included in PMC. And the Historical digitized collection has several records that are not part of PubMed.
With this difference and another important difference, it is important to search PMC separately – especially if one is authoring a systematic or a scoping review. The search engine of PMC can search the complete article whereas the search engine of PubMed can only search the metadata of an article.
I have recently helped an author with a search on road traffic accidents. This article: – Evolution of Urban Transportation Policies in India: A Review and Analysis – did not appear with a PubMed search as the journal is not included in PubMed.
If we check this article – Safer cycling in older age (SiFAr): a protocol of a randomized controlled trial – this does not have the words – road accidents – in the title or abstract, but the phrase appears in the full text!
Some important tips:
- To search for a word, phrase or number in the full article, tag your search term with [article]
- PubMed allows us to search for our terms in the title and abstract, together – with the tag [tiab]. In PMC – we need to search them with separate tags [ti] and [ab]
I learnt about the importance of searching PMC separately only recently. I thought I should share this with all!