tarting about July 2005, NLM will be including the ClinicalTrials.gov identifier number in MEDLINE records, when that information appears in the original publication. For background information please see the International Committee of Medical Journal Editors (ICMJE) Web site for their editorial and updates on the topic of registering clinical trials before publication of the results. The ICMJE recommends that the clinical trial registration number be included at the end of the article's abstract.

The data will also appear in PubMed in the Secondary Source ID list in the Citation display, in the SI field of the MEDLINE tagged display, and in the DataBankList elements of the XML display. The general display format for the data is: an alphabetic label of ClinicalTrials.gov followed by a slash and then an 11-digit alphanumeric string starting with NCT followed by eight numbers. An example in the Citation format display would be:

Secondary Source ID:

• ClinicalTrials.gov/NCT00000161

If there are multiple ClinicalTrials.gov numbers mentioned in one journal article, all will be added to the MEDLINE record.

In PubMed, the data will be searchable using the [si] search tag; each of the pieces or the entire string is searchable, e.g.:

nct00000161 [si]

clinicaltrials.gov [si]

clinicaltrials.gov/nct00000161 [si]

Use "clinicaltrials.gov [si]" to retrieve all citations to articles listing trial registration in ClinicalTrials.gov regardless of which particular trial is involved.

By Sara Tybaert
MEDLARS Management Section
and
By Lou Wave S. Knecht
Bibliographic Services Division

Tybaert S, Knecht LS. ClinicalTrials.gov Identifier to be Added to MEDLINE^®/PubMed^® Data. NLM Tech Bull. 2005 May-Jun;(344):e13.