Since 1975, NLM has included author-written abstracts from journals whose publishers gave the NLM permission for their use. These abstracts appear in the Abstract (AB) field. Over 50% of the documents in Ovid HealthSTAR (R) contain abstracts.

The abstract index contains all searchable words from the abstract.

All Fields (AF) is an alias for all of the fields which occur in the source documents, including value-added fields such as MeSH Subject Headings (SH).

Author NameID (AI) field contains author's full name and its unique identifiers may be supplied by the publisher for records added or updated beginning in January 2013. The identifier may be an Open Researcher and Contributor ID (ORCID), an International Standard Name Identifier (ISNI), Ringgold, or from the Virtual International Authority File (VIAF).

The Abstract Label (AL) field contains the valid label name found in published Structured Abstracts (e.g., Introduction, Goals, Study Design, Findings, and Discussion). Each label has a corresponding broader NLM Category (NC) map, and an indication of whether the label is classed as an "Ending Label" concept. This is word indexed and is displayed in the Abstract (AB) field.

The Abbreviated Source (AS) field includes a display of all the basic information needed to locate a citation, including the Journal Abbreviation (JA), the Volume (VO), Issue/Part (IP), Page (PG), and Date of Publication (DP).

The Authors (AU) field contains the authors of the article. The format for authors is last name followed by one or more initials: Smith JC or Smith J. Enter the last name, or if it is a common name, enter the last name and first initial. If you are unsure of the spelling of the last name (macdonald or mcdonald), enter one version and then scroll through the list of names to find the other.

Misspelled and corrected names are now included in the Author Index to ensure all possible matches. Only correct author names display, while incorrectly spelled names are indexed along with the correct spelling of the name.

The Author Last Name (AX) index allows you to search for the authors’ last names. Author names display in Authors (AU) and Authors Full Name (FA) fields.

The Cited Reference DOI (CD) field contains the DOI information of the source citation.

This field displays in the Cited References (RF) field.

The Cited Reference Volume (CE) field contains the particular volume of the Cited Reference Source (CS).

It displays in the Cited References (RF) field.

The Cited Reference Page (CG) field contains the page information of the source citation.

It displays in the Cited References (RF) field.

The Conflict of Interest (CI) field contains disclosure statements as provided by the publisher. This field was introduced in 2017.

The Country of Publication (CP) index contains the full name of the country in which an article was published. The country name is entered into the index as a phrase.

The Cited Reference Date (CQ) field contains at least the publication year for the respective reference. This field may contain month, day and/or time of publication or release.

This field displays in the Cited References (RF) field.

The Copyright Index (CR) index contains published information and it will be display at the end of Abstract (AB) or Other Abstract (OA) field if available. The Copyright Index (CR) is a word indexed.

The Cited Reference Source (CS) field contains the journal name of the source citation.

The Cited Reference Source displays in the Cited References (RF) field.

The Cited Reference PMCID (CZ) field contains the PMC identification number of the source citation reference.

It displays in the Cited References (RF) field.

The MeSH Date (DA) field contains the date MeSH terms were added to the citation. The MeSH date is the same as the Entrez date until MeSH are added. This field has a format display of YYYY/MM/DD HH:MM and the index format is YYYYMMDD.

The Publisher Item Identifier (DI) field uniquely identifies individual published documents that are provided by the publisher for new citation submitted. The full PII appears as such e.g "S0036-36342008000600005"

Search all PII's by replacing punctuation with spaces such as "S0036 36342008000600005".di. for the displayed PII of S0036-36342008000600005.

The DOI (DO) field contains the Digital Object Identifier - a unique and persistent digital identification code for any object of intellectual property. The DOI itself consists of two parts: a prefix which is assigned to each publisher by the administrative DOI agency, e.g., "10.1097", and a suffix which is assigned by the publisher and can be any code that the publisher chooses, e.g., "00045415-200111000-00002". The full DOI appears as such: "10.1097/00045415-200111000-00002".

Search all DOI's by replacing punctuation with spaces such as "10 1016 j adnc 2003 08 001".do. for the displayed DOI of 10.1016/j.adnc.2003.08.001. (all DOI information provided to Ovid is loaded as it becomes available from NLM).

The Date of Publication (DP) field consists of the date of publication for a citation, in the format YYYY MMM DD (1950 dec 3). The Month and day are not always present. This field is also displayed as part of the Source (SO) field.

The Create Date (DT) field contains the date when it was added to PubMed. It was implemented with all PubMed records when the 2009 system became available on December 15, 2008. All records added to PubMed prior to implementation received a Create Date equal to Entrez Date (EZ). This field has a format display of YYYY/MM/DD HH:MM and the index format is YYYYMMDD.

The Equal Contributor (EC) field contains the journal publisher names who submit citation data to Pubmed.

The Entry Date (ED) field contains the NLM internal Date Completed (DCOM) which is the date processing of the record ends; i.e., MeSH Headings have been added, quality assurance validations are completed, and the completed record subsequently is distributed to PubMed. This is contrasted with the PubMed/MEDLINE Date Created, which is the date processing begins.

The Electronic Date of Publication (EP) is the date the record was sent to NLM for inclusion in HealthSTAR (R). This index appears in the format YYYYMMDD.

The ISSN Electronic (ES) field contains the Electronic International Standard Serial Number (EISSN) for the journal in which an article was published. It appears as an 8 digit number, separated by a hyphen: 0028-4793. To retrieve all of the articles for a journal, search by the Journal Name (JN).

Both Electronic and Print ISSN can be searched in the IS index.

The Entrez Date (EZ) is the date the citation was added to PubMed. However, prior to October 9, 2008, the Entrez Date was set equal to the Publication Date (DP) on records with publication dates before September 1997. Beginning on October 9, 2008, the Entrez Date is set equal to the Publication Date (DP) when the record enters PubMed more than twelve months after the date of publication. This field has a format display of YYYY/MM/DD HH:MM and the index format is YYYYMMDD.

The Authors Full Name (FA) field contains the full name of the authors of the article when available.

Subheadings are qualifiers added to MeSH subject headings to refine their meaning. Terms such as "etiology" or "therapy", when combined with a MeSH heading, give a precise idea of what an article covers.

The Floating Subheadings (FS) field contains both the 2-letter codes, such as "po" and the full headings, such as "poisoning". These are displayed following the corresponding MeSH Subject Headings.

Sometimes you may wish to retrieve every Floating Sub-heading that includes a particular word; this is done by searching the single word in the Floating Sub-heading Word (FX) field.

The Grant Country (GC) field contains the country of the organization that awarded the grant.

This field displays as part of the Grant Information (GI) field.

The Grant Information (GI) field displays information about awarded grants, may contain Grant Number (NO), Grant Acronym (GR), Grant Organization (GO) and Grant Country (GC).

The Grant Organization (GO) field contains the full name of the organization that has awarded the grant.

This field displays as part of the Grant Information (GI) field.

The Grant Acronym (GR) field contains the acronym of the organization that has awarded the grant.

This field displays as part of the Grant Information (GI) field.

The Gene Symbol (GS) field contains Gene Symbols as they are entered into Ovid HealthSTAR (R) in the original document. They often, but not always, conform to standardized human gene nomenclature. Ignore super or sub-scripts in entry of a gene symbol: psub 1450 would be entered p1450. Enter hyphens as in the original symbol.

The Gene Symbol field was added to Ovid HealthSTAR (R) in 1991. Beginning in 1996, data will no longer be added to this field.

The Gene Word (GW) index contains individual words from the Gene Symbol (GS) field. The Gene Symbol field was added to Ovid HEALTHSTAR (R) in 1991. Beginning in 1996, data will no longer be added to this field.

The Subject Heading Word (HW) index allows you to retrieve every MeSH subject heading that includes a particular word. Do this by searching a single word in the Subject Heading Word (HW) field.

The Investigator Affiliation (IA) field contains author's full name and its affiliation to the investigator of the article.

The Article Identifier (ID) field may contain an identifier that links with records in the publisher's system. The Article Identifier values may include the controlled publisher identifier (PII) or the digital object identifier (DOI). It is most often used for LinkOut, and is not considered part of the citation source information.

The Indexing Method (IG) field was introduced by the NLM in September 2018. It will only be present in records if a value is specified. If Indexing Method is not present in the records, the indexing method is fully human indexed.

Values for Indexing Method (IG) are:
Curated - MeSH indexing method is provided algorithmically and a human reviewed (and possibly modified) the algorithm results.
Automated - MeSH indexing is provided algorithmically.

The ISSN Linking (IL) index contains an identifier intended to provide a mechanism to group the various medium versions of a continuing resource. The purpose of the ISSN-L is to provide a mechanism for grouping, or collocating, the various medium versions of a resource, for instance, the print and online versions of a journal per ISO 3297 standards.

The first ISSN assigned, in the ISSN Register, to any medium version of a continuing resource shall be designated by default to function also as the ISSN-L and shall apply to all other media versions of that resource identified in the ISSN Register.

The ISSN Linking field will be used only for new records added during the 2008 production year (although NLM still does not know the timing when all will be in place to start to appear on records).

The Institution (IN) field contains all author full names and their affiliations, which is usually the source for a reprint of the article. This information can be searched in most documents since 1988, but records from earlier years which were added to the database after 1988 may also contain institution information. Beginning with documents indexed in 1996, author's email address will also be included, if present in the journal.

The information is taken from the source document and is not standardized. Enter the single most descriptive word in an institution (harvard, not university). Consider both full spellings and abbreviations.

The ISO Journal Abbreviation (IO) field contains journal abbreviations. Those created prior to 2007 did not necessarily conform to the ISO standard. ISO Journal Abbreviations created after this date are identical to the Journal Abbreviation (JA) field. In November 2009 ISO abbreviations were retrospectively assigned for every record from a journal that was currently indexed for MEDLINE at that time.

The Issue/part field (IP) contains the issue and/or part for a particular volume of a journal. The Issue/Part field displays as part of the Source (SO) and Abbreviated Source (AS) fields.

The Investigator (IR) field contains the NASA-funded principal investigator(s) who conducted the research. The format for authors is last name followed by one or more initials: Smith JC or Smith J.

The ISSN Print (IS) field contains the International Standard Serial Number (ISSN) for the journal in which an article was published. It appears as an 8 digit number, separated by a hyphen: 0028-4793. To retrieve all of the articles for a journal, search by the Journal Name (JN).

Both Electronic and Print ISSN can be searched in the IS index.

The Investigator NameID (IX) field is defined to contain a unique identifier associated with the name. The value in the Identifier attribute Source will designate the organizational authority that established the unique identifier.

The Journal Abbreviation (JA) field contains the abbreviation of the journal in which the article was published.

The NLM Journal Code (JC) is an alpha-numeric code established by NLM which uniquely identifies every journal indexed in the NLM databases. Only the 7 digit code is searchable, in some cases the 3 digit alpha-numeric code will display as well.

The Journal Name (JN) field contains the full name of the journal in which an article was published. This field usually displays as part of the Source (SO) field.

The Journal Word (JW) index contains individual words from every journal name in Ovid HealthSTAR (R). This index displays as part of the Source (SO) field.

The Keyword Heading Word (KF) field allows you to retrieve every Keyword Heading that includes a particular word.

The Keyword Heading (KW) field contains the Keyword Headings assigned by indexers at NLM to describe the content of an article. To retrieve every Keyword Heading that includes a particular word, search for the word in the Keyword Heading Word (KF) field.

The Language (LG) field contains the language(s) of publication of an article. The language name will appear in the index as the full form and a 3-letter code (such as fre for French) and as the full name French. The codes are usually, but not always, the first three letters of the language name.

The language index is quickly scrollable to determine all languages which appear in Ovid MEDLINE (R).

The NLM Category (NC) index defines the NLM-assigned mapped-to category of a published Structured Abstract Label (AL) (e.g., Background, Objective, Methods, Results, and Conclusions). This is word indexed but not displayable.

The NLM Journal Name (NJ) field contains the full name of the journal in which an article was published.

The Name of Substance Word (NM) index contains single words from the CAS Registry Number/Name of Substance (RN) field and is used to search portions of chemical names. This field displays as part of the CAS Registry Number/Name of Substance (RN) field.

The Name of Substance Word (NM) field was added to Ovid HEALTHSTAR (R) in 1980.

The Grant Number (NO) field contains the original identification number of the grant that is awarded to the work as described in the content. The identification number is assigned by the grant agency.

This field displays as part of the Grant Information (GI) field.

The Number of References (NR) field contains the number of bibliographic references listed in the review article.

Effective October 1, 2010 NLM discontinued the practice of including the number of bibliographic references listed in articles cited in MEDLINE. NLM had included the number of references for the following Publication Types: Review; Consensus Development Conference; Consensus Development Conference, NIH; Interactive Tutorial; Meta-Analysis. This change in policy is prospective only; we will not remove number of references data from existing citations.

This field displays in the Abstract (AB) and Title (TI) when available.

The General Note (NT) field contains general supplementary information about an item. The notes may include information on the availability of a bibliography, ordering information for dissertations or hearings, or general summaries of materials such as manuals or scripts. A series title may appear for a book or for audiovisual materials.

The Other Abstract (OA) field includes a brief abstract written by collaborating partners. The OA field is indexed in the Abstract (AB) field, and contains all searchable words from the other abstract.

Collaborating Partners include:

The Other ID (OI) is a unique alpha-numeric code. In particular, it will contain the PubMed Central Identifier (PMCID), where the alphabetical prefix 'PMC' precedes the identifier. If the publisher has embargoed access to the full text, the date of availability in PubMed Central will be noted. When the embargo is lifted, a revised record with the date of availability removed will be released.

Other ID's are entered into the index as phrases. In particular, PMC ID's should be searched as how the alpha-numeric code appears in PubMed Central (PMC).

The Organism Supplementary Concept (OS) field contains the Protocol Class 4 SCR terms that includes viruses and other organisms. The Organism Supplementary Concept (OS) terms are phrase indexed.

They appear for the first time in the 2018 MeSH and were made available as a means to index emerging viruses and other pathogenic organisms as they occur in the literature without delay.

The Original Title (OT) includes any non-English titles in the original language. If the original title was in a non-Roman alphabet, then the OT is transliterated.

The Organism Supplementary Concept Word (OX) index allows the users to retrieve single terms from the Organism Supplementary Concept (OS) field.

The Primary Author (PA) index contains the first author listed for the article. This allows users to search for articles by any primary author. Author names display in the Authors (AU) and Authors Full Name (FA) fields.

Searching for smith rh.pa. will return results where Smith RH was listed as the main author of the article.

The Page (PG) field consists of the inclusive pagination of a journal article. Often a journal title combined with the beginning page number is enough to locate a citation. You can search for pages with alphanumeric, such as "a1.pg.". This field is usually displayed as part of the Source (SO) field.

The Publication History Status (PH) field contains information from the publisher regarding important events in the publishing process. It contains a date, and one of the following values for each date in the publication history:

The Publication History Status (PH) field is word-indexed.

The PMC Identifier (PM) is a unique alpha-numeric code. In particular, it will contain the PubMed Central Identifier (PMCID), where the alphabetical prefix 'PMC' precedes the identifier. If the publisher has embargoed access to the full text, the date of availability in PubMed Central will be noted. When the embargo is lifted, a revised record with the date of availability removed will be released.

Other ID's are entered into the index as phrases. In particular, PMC ID's should be searched as how the alpha-numeric code appears in PubMed Central (PMC).

The Personal Name as Subject (PN) field displays the name of a well-known person if they are discussed in an article, such as an interview or obituary.

The Publication Status (PP) field contains the current status of the publication, as submitted by the publisher. Possible values are:

The Pubmed Central Release (PQ) field contains the embargo date associated with the availability of the published article in PMC.

The Protocol Supplementary Concept (PS) field contains the Protocol Class 2 SCR terms. These terms were previously exported in Registry Number/Name of Substance (RN) in MEDLINE/PubMed. The PS terms are phrase indexed.

With the 2011 reload, Protocol Supplementary Concept (PS) will be loaded separately only for new records added during 2011 production year

In addition to indexing documents with Medical Subject Headings, the indexers at the National Library of Medicine assign terms to describe the article type. Publication Types include such classifications as reviews, clinical trials, directories and letters. These terms appear in the Publication Type (PT) field.

To view the index, enter enough letters to distinguish a publication type (jour for "journal article"); the entire index is quickly scrollable to determine all possible publication types.

With the 2005 reload, Publication Types are also loaded into the MeSH. Because some Publication Types are also MeSH terms, the syntax to enter the Tree is "Randomized controlled trial [publication type]". To post the results from the Tree without entering the Tree, the syntax is: "Randomized controlled trial [publication type]"/ or Randomized controlled trial.pt.

The Protocol Supplementary Concept Word (PX) index allows the users to retrieve single terms from the Protocol Supplementary Concept (PS) field.

The Revision Date (RD) field contains the issue (year, month and day) in which a document was revised in Index Medicus. The RD field appears in the format YYYYMMDD. Previously, the RD field was indexed with the Entry Date (ED) field. Now, it is a separate index.

The Cited References (RF) field contains a complete or partial reference list to the source citation.

Use RF to simultaneously search in all searchable parts of the Cited References field, including Cited Reference Date (CQ), Cited Reference Author, Cited Reference Source (CS), Cited Reference Title, Cited Reference DOI (CD), Cited Reference Volume (CE), Cited Reference Page (CG), Cited Reference Issue (RP), Cited Reference PMCID (CZ), Cited Reference Publisher Identifier (RY) and Cited Reference UI (RZ).

The Reference Title Index (RL) allows the users to search for the reference(s) title which may contain one or multiple source citations.

It displays in the Cited References (RF) field.

The Registry Number/Name of Substance (RN) field contains the Chemical Abstracts Service registry number or Enzyme Commission number for a compound mentioned in an article. If the generic compound name could be determined, then it is also included.

The Registry Number/Name of Substance (RN) field was added to Ovid HealthSTAR (R) in 1980.

The Record Owner (RO) field contains the owner of the record.

The Cited Reference Issue (RP) field contains the issue information of the journal in which the citation appears.

It displays in the Cited References (RF) field.

The Rare Disease Supplementary Concept (RS) field contains the Protocol Class 3 SCR terms. The RS terms are phrase indexed.

Beginning with 2011 Healthstar data, Rare Disease Class 3 SCRs are also going to be exported.

The Rare Disease Supplementary Concept Word (RX) index allows the users to retrieve single terms from the Rare Disease Supplementary Concept (RS) field.

The Cited Reference Publisher Identifier (RY) field contains the Publisher Item Identifier (DI) of the source citation.

It displays in the Cited References (RF) field.

The Cited Reference UI (RZ) field contains the PMID of the source citation.

It displays in the Cited References (RF) field as part of the link URL to NLM.

The Secondary Source AN (SA) index contains the unique identifiers of outside resources discussed in MEDLINE articles. The display will include the Secondary Source ID (SI) and the unique identifier seperated by a forward slash (RefSeq/NM_020533). If you wish to search all works from a particular data bank use the Secondary Source ID (SI) index: refseq.si.

The Journal Subset (SB) field identifies the subset for MEDLINE records from certain journal lists on specialized topics. The NLM discontinued the Journal Subset (SB) indexing for MEDLINE/PubMed with the 2022 reload, with the exception of index medicus.sb. and oldmedline citations.sb.. Ovid replaced the corresponding Journal subset limits new journal selections based on NLM Catalog searches, using matching MeSH terms and title words to create new lists of titles for the below journal subsets. We strongly recommend that you review your search strategies if you used the Journal Subset (SB) field, or limits in search strategies prior to the 2022 reload.

Do not confuse these journal subsets with the Topics subsets available on PubMed's Limits screen, which are search strategies.

The Season (SE) field contains the month or season that the citation article was published. The field usually consists of a three-character alphabetic abbreviation of the month or season.

Example: Win

The MeSH Subject Headings (SH) field contains the Medical Subject Headings used by indexers at the National Library of Medicine (NLM) to describe the content of an article. NLM's MeSH terms are organized in a hierarchy, or "tree" structure.

The Secondary Source ID (SI) identifies secondary source databanks with unique identifiers of outside resources discussed in MEDLINE articles. The field is composed of the source acronym: GENBANK

The Secondary Source ID (SI) formerly known as the Molecular Sequence (MS) field was added to Ovid MEDLINE (R) in 1988.

The Secondary Source Link (SL) index contains the URL to the outside resources discussed in MEDLINE articles when the Secondary Source ID is either ClinicalTrials.gov or ISRCTN. The index contains the the URL, for searching ease use the Secondary Source AN (SA) index: nct00000150.sa.

The Source (SO) field includes a display of all the basic information needed to locate a record, including the full Journal Name (JN), Volume (VO), Issue/Part (IP), Page (PG), and Date of Publication (DP).

The Synonyms (SY) field contains a synonymous name for generic drug names that are not actual trade names.

The Title Comment (TC) field pertain to and contain citations to associated journal publications, e.g., comments, errata, retractions, or cited references. These data enable links between the record at hand and its associated citations.

This field begins with the indication of comment or correction type (see Comments (CM) fields for a full list of types) and then displays the Journal Abbreviation (JA), Date of Publication (DP), Volume (VO), Issue/Part(IP) and Page (PG).

The Title (TI) field contains the English language version of a title. For documents which were not written in English, the original or transliterated title appears in a separate field, Original Title.

The title sometimes includes notes, in brackets, about the article, such as an indication that it is a letter, editorial, or comment.

The Text Word (TW) field is an alias for all of the fields in a database which contain text words and which are appropriate for a subject search.

The Text Word field in HealthStar includes Title (TI) and Abstract (AB).

The Unique Identifier (UI) field contains the PMID (PubMed identifier or PubMed unique identifier) that is the unique number assigned to each PubMed record.

PMIDs do not change over time or during processing and are never reused.

The Update Date (UP) field contains the date the record was added to Ovid's HealthSTAR (R) since reload completion. The Update Date for existing records changes with each global reload to reflect the date starts processing the reload data. The UP field appears in the format YYYYMMDD.

The Volume (VO) field consists of the volume and issue of a serial publication. This field is usually displayed as part of the Source (SO) field.

The Exploded MeSH Heading (XM) index contains pre-exploded MeSH Headings. MeSH Subject Headings are hierarchical, with up to twelve levels of narrower terms from the top of a hierarchy. In order to retrieve a term and all of its narrower terms, a subject heading must be "exploded", that is, the subject heading and allnarrower terms are "OR'd" together. OVID pre-explodes highly-posted broader terms with their narrower terms during loading. These pre-exploded MeSH Headings display in the MeSH Subject Headings (SH) field.

The Exploded Subheadings (XS) index contains the two-letter codes for the pre-exploded subheadings. Sometimes multiple MeSH Subheadings can be logically grouped together. Such related groups of subheadings are "pre-exploded" under one broad subheading. This means that all the grouped subheadings can be retrieved together by searching on the "pre-exploded" version of the broad subheading. These pre-exploded MeSH Headings display in the MeSH Subject Headings (SH) field.

The Year of Publication (YR) field contains the year in which an article or monograph was published. Only the four digit year is contained in the index.