The PMCID and NIHMSID Fields

Unlike most of the fields described in this section, the PMCID and NIHMSID fields are not generic fields. They occur only in the Journal Article and Electronic Article reference types.  As you can see below, the generic names for these fields are Custom 2 and Custom 6.

The U.S. National Institutes of Health (NIH) requires that the PMCID be reported by some authors, so it is important to track this information and be able to use it if you are working with the NIH. You can find information on requirements for using these numbers at https://publicaccess.nih.gov/include-pmcid-citations.htm.

What is the difference between these two? The PMCID is the unique permanent identifier assigned when an article is approved for publication at PubMed Central (PMC). The NIHMSID is a temporary identifier assigned when an article is submitted for publication at PubMed Central. The NIHMSID is only to be used for the first 90 days after it is assigned or until an article has been granted a PMCID. You can find more information on this at https://www.ncbi.nlm.nih.gov/pmc/about/public-access-info/.

Note: The PMID is not equivalent to either of these numbers. The PMID is the unique identifier for an article in the PubMed database and would be imported into the Accession Number field when importing references from PubMed, or into the Notes field when importing references from the Web of Science.