30 International Information Systems: Services and Products: MEDLARS / MEDLINE

Shalini Lihitkar Waghmare

I.  Objectives

In this module, we will learn about the (MEDLARS) / MEDLINE, its history, products and services. After reading this module you will be able to know the importance of MEDLARS and its services in Medical Sciences.

II.   Learning Outcome

After studying this module, you will learn about the (MEDLARS)/MEDLINE, its history, products and services. After reading this module you will be able to know the importance of MEDLARS and its services in Medical Sciences. You will learn that MEDLINE is a huge database of over 20 million references to articles published in approximately 5,600 current biomedical journals from the United States and over 80 foreign countries. It is a database you can search free using the NLM PubMed system at http://pubmed.gov. It is used for finding references on specific medical topics using either keywords or MeSH for references to articles published in the 1940’s – to the present as converted from Current List of Medical Literature (CLML). Medline Plus is the National Library of Medicine’s web site for consumer health information. Lastly, you will be informed that PubMed citations come from MEDLINE indexed journals, journals/manuscripts deposited in PMC, and from NCBI Bookshelf. Both MEDLINE and other PubMed citations may have links to full-text articles or manuscripts.

III.   Module Structure

1.       Introduction

2.      History

3.      MEDLINE

3.1     National Centre for Biotechnology Information

3.2    Retrieval from MEDLINE

3.2.1  MeSH

3.3     MEDLINE Usage

3.4     Broad Subject Coverage

3.5     MedlinePlus (http://medlineplus.gov/)

4.       PubMED

5.       PubMED Central

6.       Differnce Between MEDLINE, PubMED, and PMC (PUBMED Central)

7.       Unified Medical Language System (UMLS)

8.       ICMR-NIC Centre for Biomedical Information

8.1      IndMED Database

8.2     MedIND

9.       Summary

10.      References

1.  Introduction

MEDLINE (Medical Literature Analysis and Retrieval System Online, or MEDLARS Online) is  a  bibliographic  database  of  life  sciences  and  biomedical  information.  It  includes bibliographic information for articles from academic journals covering medicine, nursing, pharmacy, dentistry, veterinary medicine, and health care. It was established in 1964 as MEDLARS (Medical Literature Analysis and Retrieval System), a computerized storage and retrieval system at the US’s National Library of Medicine (NLM) to  provide  for  bibliographic  access  to  the  NLM’s  large  biomedical  literature  collection. MEDLINE also covers much of the literature in biology and biochemistry, as well as fields such as molecular evolution. Compiled by the   National Library of Medicine (NLM) of United States, MEDLINE is freely available on the Internet and is searchable via PubMed and NLM’s National Centre for Biotechnology Information’s Entrez system.

MEDLARS, as a project grew out of the National Library of Medicine Index Mechanization Project of 1958-60. The system operated at the beginning of 1964. MEDLARS is a computerized information retrieval system with three major types of products: (i) one-shot demand searches on questions of great complexity, (ii) recurring bibliographies in special fields of the medical sciences, and (iii) composition of a comprehensive periodical index, the Index Medicus.

2.  History

The National Library of Medicine (NLM), on the campus of the National Institutes of Health in Bethesda, Maryland, has been a centre of information innovation since its founding in 1836. The world’s largest biomedical library, NLM maintains and makes available a vast print collection and produces electronic information resources on a wide range of topics that are searched billions of times each year by millions of people around the globe. It also supports and conducts research, development, and training in biomedical informatics and health information technology. In addition, the Library coordinates a 6,000-member National Network of Libraries of Medicine that promotes and provides access to health information in communities across the United States.

MEDLARS (Medical Literature Analysis and Retrieval System) is a  computerised biomedical bibliographic retrieval system. It was launched by the National Library of Medicine in 1964 and was the first large scale, computer based, retrospective search service available to the general public. Since 1879, the National Library of Medicine has published Index Medicus, a monthly guide to medical articles in thousands of journals. The huge volume of bibliographic citations were manually compiled. In 1957 the staff of the NLM begun to plan the mechanization of the Index Medicus; what was needed was a way to manipulate all this information to produce subsidiary products. By 1960 a detailed specification was prepared and by the spring of 1961 a request for proposals was sent out to 72 companies to develop the system. As a result a contract was awarded to the General Electric Company. The computer (a Minneapolis-Honeywell 800) which was to run MEDLARS was delivered to the NLM in March 1963. MEDLARS cost $3 million  to develop and at the time of its completion in 1964, no other publicly available, fully operational electronic storage and retrieval system of its magnitude existed. The original computer configuration operated from 1964 until its replacement by MEDLARS II in January 1975. Input sources into MEDLARS included Biomedical and other health science Journals, books, technical reports, etc.

In late 1971, an online version called MEDLINE (“MEDLARS Online”) became available as a way to do online searching of MEDLARS from remote medical libraries. This early system covered 239 journals and boasted that it could support as many as 25 simultaneous online users (remotely logged-in from distant medical libraries) at one time. However, this system remained primarily in the hands of libraries, with researchers able to submit pre-programmed search tasks to librarians and obtain results on printouts, but rarely able to interact with the NLM computer output in real-time. This situation continued through the beginning of the 1990s and the rise of the World Wide Web.

In 1996, soon after most home computers began automatically bundling efficient web browsers, a free public version of MEDLINE was instigated. This system, called PubMed, was offered to the general online user in June, 1997, when MEDLINE searches via the Web were demonstrated.

3.  MEDLINE

MEDLINE is the U.S. National Library of Medicine’s (NLM) premier bibliographic database that contains over 23 million (in 2016) references to journal articles in life sciences with a concentration on biomedicine. A distinctive feature of MEDLINE is that the records are indexed with NLM Medical Subject Headings (MeSH). The great majority of journals are selected for MEDLINE based on the recommendation of the Literature Selection Technical Review Committee (LSTRC), an NIH-chartered advisory committee of external experts analogous to the committees that review NIH grant applications. Some additional journals and newsletters are selected based on NLM-initiated reviews, e.g., history of medicine, health services research, AIDS, toxicology and environmental health, molecular biology, and complementary medicine, that are special priorities for NLM or other NIH components. These reviews generally also involve consultation with an array of NIH and outside experts or, in some cases, external organizations with which NLM has special collaborative arrangements.

MEDLINE is the primary component of PubMed, part of the Entrez series of databases provided by the NLM National Center for Biotechnology Information (NCBI). MEDLINE database contains over 20 million references to journal articles in life sciences with a concentration on biomedicine. A distinctive feature of MEDLINE is that the records are indexed with NLM Medical Subject Headings (MeSH). MEDLINE is also the primary component of PubMed, part of the Entrez series of databases provided by the NLM- National Center for Biotechnology Information (NCBI). The time coverage of the database is 1946 to the present, with some older material. MEDLINE, therefore, functions as an important resource for biomedical researchers. More than 5,600 (in 2016) biomedical journals are indexed in MEDLINE.

3.1  National Centre for Biotechnology Information

This centre was created by Public Law of United States of America in 1988 as part of National Library of Medicine at National Institute of Health, Bethesda, Maryland to:

•    Create automated systems for knowledge about molecular biology, biochemistry, and genetics.

•    Perform research into advanced methods of analyzing and interpreting  molecular biology data.

•    Enable biotechnology researchers and medical care personnel to use the systems and methods developed.

This centre is supported by:

a.  MEDLINE

•    Citations to Articles in 5,600 Biomedical Journals Selected by an Expert Panel

•    Subject Specialists Add NLM’s Medical Subject Headings (MeSH) to Each Citation

b.  PubMed

•    MEDLINE Database Plus Supplementary Material From Some MEDLINE Journals

•    A Component of a Larger Retrieval System, Entrez

c.  Entrez

•    Integrates Access to Biomedical Literature and a Collection of Molecular Biology Databases

3.2  Retrieval from MEDLINE

MEDLINE uses Medical Subject Headings (MeSH) for information retrieval. Engines designed to search MEDLINE (such as Entrez and PubMed) generally use a Boolean expression combining MeSH terms, words in abstract and title of the article, author names, date of publication, etc. Entrez and PubMed can also find articles similar to a given one, based on a mathematical scoring system that takes into account the similarity of word content of the abstracts and titles of two articles.

3.2.1 MeSH

MeSH, the Medical Subject Headings comprise NLM’s controlled vocabulary used for indexing articles, for cataloging books and other holdings, and for searching MeSH-indexed databases, including MEDLINE. MeSH terminology provides a consistent way to retrieve information that may use different terminology for the same concepts. MeSH organizes its descriptors in a hierarchical structure so that broad searches will find articles indexed more narrowly. This structure also provides an effective way for searchers to browse MeSH in order to find appropriate descriptors. The MeSH vocabulary is continually updated by subject specialists in various areas. Each year hundreds of new concepts are added and thousands of modifications are made.

3.3  MEDLINE Usage

PubMed usage has been on the rise since 2008. A service such as MEDLINE strives to balance usability with power and comprehensiveness. In keeping with the fact that MEDLINE’s primary user community is professionals (medical scientists, health care providers), searching MEDLINE effectively is a learned skill as untrained users are sometimes frustrated with the large numbers of articles returned by simple searches. Counter intuitively, a search that returns thousands of articles is not guaranteed to be comprehensive. Unlike using a typical Internet search engine, PubMed searching of MEDLINE requires a little investment of time. Using the MeSH database to define the subject of interest is one of the most useful ways to improve the quality of a search. Using MeSH terms in conjunction with limits (such as publication date or publication type), qualifiers (such as adverse effects or prevention and control), and text-word searching is another.

The great majority of journals are selected for MEDLINE based on the recommendation of the Literature Selection Technical Review Committee (LSTRC), an NIH-chartered advisory committee of external experts analogous to the committees that review NIH grant applications. Some additional journals and newsletters are selected based on NLM-initiated reviews, e.g., history of medicine, health services research, AIDS, toxicology and environmental health, molecular biology, and complementary medicine, that are special priorities for NLM or other NIH components. These reviews generally also involve consultation with an array of NIH and outside experts or, in some cases, external organizations with which NLM has special collaborative arrangements.

3.4 Broad Subject Coverage

The subject scope of MEDLINE is biomedicine and health, broadly defined to encompass those areas of the life sciences, behavioural sciences, chemical sciences, and bioengineering needed by health professionals and others engaged in basic research and clinical care, public health, health policy development, or related educational activities. MEDLINE also covers life sciences vital to biomedical practitioners, researchers, and educators, including aspects of biology, environmental science, marine biology, plant and animal science as well as biophysics and chemistry. Increased coverage of life sciences began in 2000.

The majority of the publications covered in MEDLINE are scholarly journals; a  small number of newspapers, magazines, and newsletters considered useful to particular segments of the NLM broad user community are also included.

MEDLINE is the primary component of PubMed (http://pubmed.gov). The result of a MEDLINE / PubMed search is a list of citations (including authors, title, source, and often an abstract) to journal articles and an indication of free electronic full-text availability. Searching is free of charge and does not require registration.

A growing number of MEDLINE citations contain a link to the free full text of the article archived in PubMed Central or to other sites. Linking can be made from many MEDLINE references to the Web site of the publisher or other full text provider to request or view the full article, depending upon the publisher’s access requirements. For articles not freely available on the Web, the “Loansome Doc” feature in PubMed provides an easy way to place an electronic order through the National Network of Libraries of Medicine (NN/LM) for the full-text copy of an article cited in MEDLINE. Registration is required and local fees may apply for this service.

Services/products providing access to MEDLINE data are also developed and made available by organizations that lease the database from NLM. Access to various MEDLINE services is often available from medical libraries, many public libraries, and commercial sources.

3.5  MedlinePlus (http://medlineplus.gov/)

It is the National Library of Medicine’s web site for consumer health information. The site offers authoritative, up-to-date health information, without advertisements, and is available anytime, anywhere for free. A Spanish-language version, MedlinePlus en español (http://medlineplus.gov/spanish), is also available. A site for cell phones and other mobile devices is at http://m.medlineplus.gov. MedlinePlus is not an exhaustive list of every health web resource. It is a selective list of authoritative health information sources from NIH and other government and professional organizations in the U.S.

4.    PubMED

PubMed is a free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine (NLM) at the National  Institutes  of  Health  maintains  the  database  as  part  of the Entrez system of information retrieval. From 1971 to 1997, MEDLINE online access to the MEDLARS computerized database had been primarily through institutional facilities like medical libraries. PubMed, first released in January 1996, ushered in the era of private, free, and home-computerized MEDLINE searching. The PubMed system was offered free to the public in June 1997, when MEDLINE searches via the web were demonstrated.

PubMed comprises of more than 26 (in 2016) million citations for biomedical literature from MEDLINE, life science journals and online books. Citations include links to full-text content from PubMed Central and publisher web sites. PubMed citations and abstracts include the fields of biomedicine and health, covering portions of the life sciences, behavioral sciences, chemical sciences, and bioengineering. PubMed also provides access to additional relevant web sites and links to the other NCBI molecular biology resources. PubMed is a free resource that is developed and maintained by the National Center for Biotechnology Information (NCBI), at the U.S. National Library of Medicine (NLM), located at the National Institutes of Health (NIH). Publishers of journals can submit their citations to NCBI and then provide access to the full-text of articles at journal web sites using LinkOut.

5.  PubMED Central

PubMed Central (PMC) is a free archive of biomedical and life sciences journal literature at the U.S. National Institute of Health’s National Library of Medicine (NIH/NLM). In keeping with NLM’s legislative mandate to collect and preserve the biomedical literature, PMC serves as a digital counterpart to NLM’s extensive print journal collection. Launched in February 2000, PMC was developed and is managed by NLM’s National Center for Biotechnology Information (NCBI). As an archive, PMC is designed to provide permanent access to all of its content, even as technology evolves and current digital literature formats potentially become obsolete. NLM believes that the best way to ensure the accessibility and viability of digital material over time is through consistent and active use of the archive. For this reason, free access to all of its journal literature is a core principle of PMC.

PMC is a repository for journal literature deposited by participating publishers, as well as for author manuscripts that have been submitted in compliance with the Public Access Policy mandated by NIH and similar policies of other research funding agencies. PMC is not a publisher and does not publish journal articles itself. PMC offers publishers a number of ways in which to participate and deposit their content in the archive. Although free access is a requirement, publishers can delay the release of their material in PMC for a reasonable period after publication. Publishers may also obtain a copy of their deposit material at any time, at no cost.

In addition to its role as an archive, the value of PMC lies in its capacity to store and cross- reference data from diverse sources using a common format within a single repository. With PMC, a user can quickly search the entire collection of full-text articles and locate all relevant material. PMC also allows for the integration of its literature with a variety of other information resources that can enhance the research and knowledge fields of scientists, clinicians and others. NLM is collaborating internationally with other agencies that share the goals of PMC. Maintaining copies of PMC’s literature in other reliable international archives that operate on the same principles provides greater protection against damage or loss of the material. At the same time, the diversity of sites allows for the possibility of more and even greater innovation, ensuring the permanence of PMC over the long-term.

6.  Difference between MEDLINE, PubMED, and PMC (PUBMED Central)

As per the fact sheet MEDLINE is the National Library of Medicine (NLM) journal citation database. Started in the 1960s, it now provides over 22 (in 2016) million references to biomedical and life sciences journal articles back to 1946. MEDLINE includes citations from over 5,600 scholarly journals published around the world. Publishers submit journals to an NIH-chartered advisory committee, the Literature Selection Technical Review Committee (LSTRC), which reviews and recommends journals for MEDLINE. The LSTRC considers the quality of the scientific content of a journal, including originality and the importance of the content for the MEDLINE global audience, using the guidelines found on the NLM Fact Sheet MEDLINE Journal Selection. The MEDLINE database is directly searchable from NLM as a subset of the PubMed database as well as through other numerous search services that license the data. In addition to the comprehensive journal selection process, what sets MEDLINE apart from the rest of PubMed is the added value of using the NLM controlled vocabulary, Medical Subject Headings (MeSH), to index citations.

PubMed has been available since 1996. Its over 25 (in 2016) million references include the MEDLINE database plus the following types of citations:

•    In-process citations, which provide records for articles before those records go through quality control and are indexed with MeSH or converted to out-of-scope status.

•    Citations to articles that are out-of-scope (e.g., covering plate tectonics or astrophysics) from certain MEDLINE journals, primarily general science and general chemistry journals, for which only the life sciences articles are indexed with MeSH.

•    “Ahead of Print” citations that precede the article’s final publication in a MEDLINE indexed journal.

•    Citations that precede the date that a journal was selected for MEDLINE indexing (when supplied electronically by the publisher).

•    Pre-1966 citations that have not yet been updated with current MeSH and converted to MEDLINE status.

•    Citations  to  some  additional  life  sciences  journals  that  submit  full  text  to  PMC (PubMed Central) and receive a qualitative review by NLM.

•    Citations to author manuscripts of articles published by NIH-funded researchers.

•    Citations for the majority of books available on the NCBI Bookshelf (a citation for the book and in some cases each chapter of the book).

PubMed citations often include links to the full-text article on the publishers’ Web sites and/or in PMC and the Bookshelf. MEDLINE is the largest subset of PubMed. You may limit your PubMed search retrieval to MEDLINE citations by restricting your search to the MeSH controlled vocabulary or by using the Journal Categories filter called MEDLINE.

PMC (PubMed Central) launched in 2000 as a free archive for full-text biomedical and life sciences journal articles. PMC serves as a digital counterpart to the NLM extensive print journal collection; it is a repository for journal literature deposited by participating publishers, as well as for author manuscripts that have been submitted in compliance with the NIH Public Access Policy and similar policies of other research funding agencies. Some PMC journals are also MEDLINE journals. For publishers, there are a number of ways to participate and deposit their content in this archive, explained on the NLM Web pages Add a Journal to PMC and PMC Policies. Journals must be in scope according to the NLM Collection Development Manual. Although free access is a requirement for PMC deposit, publishers and individual authors may continue to hold copyright on the material in PMC and publishers can delay the release of their material in PMC for a short period after publication. There are reciprocal links between the full text in PMC and corresponding citations in PubMed. PubMed citations are created for content not already in the MEDLINE database. Some PMC content, such as book reviews, is not cited in PubMed.

7.  Unified Medical Language System (UMLS)

The UMLS integrates and distributes key terminology, classification and coding standards, and associated resources to promote creation of more effective and interoperable biomedical information systems and services, including electronic health records.

The purpose of the National Library of Medicine Unified Medical Language System (UMLS) is to facilitate the development of computer systems that behave as if they “understand” the meaning of the language of biomedicine and health. The UMLS provides data for system developers as well as search and report functions for less technical users.

There are three UMLS Knowledge Sources:

•    The Metathesaurus, which contains over one million biomedical concepts from over 100 source vocabularies,

•    The   Semantic   Network,   which   defines   133   broad   categories   and   fifty-four relationships between categories for labelling the biomedical domain, and

•    The SPECIALIST Lexicon & Lexical Tools, which provide lexical information and programs for language processing.

They are distributed with flexible lexical tools and MetamorphoSys, the UMLS install and customization program.

8.  ICMR-NIC Centre for Biomedical Information

ICMR-NIC Centre for Biomedical Information also referred to as Indian MEDLARS Centre (IMC) was set up in 1986 to cater to information needs of biomedical professionals in India.

The main aim of setting up Indian MEDLARS Centre was to provide access to relevant biomedical information, in the shortest possible time, to the medical professionals. It provides information from NLM’s databases plus from other internet resources and CD databases. Support services like training, full-text of journal articles and Union Catalogue of Biomedical Periodicals are also available. The information needs in this subject are taken care of two major resources from the centre as below.

8.1  IndMED Database

IMC has designed and developed a bibliographic database of peer reviewed Indian medical journals referred to as IndMED, a database developed to cover non-Medline journals. The database includes journals from 1985 to date. There are simple and advanced search mode available for searching the database. The IndMED database is a bibliographic database developed on the lines of the MEDLINE database using the concepts of both keywords as well free-text searching. A user-friendly search engine has been designed enabling the users to access the database using “Simple” or “Advanced” search modes.

8.2  MedIND

MedIND provides online access to full-text of Indian biomedical periodicals to the users in and outside India. IndMED indexes Indian Biomedical journals. It is accessible from (http://indmed.nic.in) to the medical professionals, free of cost. The database aims at covering peer-reviewed journals from 1985 onwards. To supplement IndMED with full text of articles, this resource was developed to host full-text of indexed Indian biomedical journals. This medIND portal is accessible free of cost to the medical community in India as well those outside the country. Journals indexed in IndMED database are included in this database. At present there are no charges for hosting the journals contents on the site. Editors of journals covered in Index Medicus (MEDLINE) are welcome to have their journals included in this full-text database.

9.  Summary

In this module, we have discussed MEDLINE and its related databases. MEDLINE is a huge database of over 20 million references to articles published in approximately 5,600 current biomedical journals from the United States and over 80 foreign countries. It is a database you can search free using the NLM PubMed system at http://pubmed.gov. It is used for finding references on specific medical topics using either keywords or Medical Subject Headings (MeSH) for references to articles published in the 1940’s – to the present as converted from Current List of Medical Literature (CLML). Medline Plus) is the National Library of Medicine’s web site for consumer health information.

In conclusion, PubMed citations come from firstly MEDLINE indexed journals, secondly from journals/manuscripts deposited in PMC, and lastly from NCBI Bookshelf. Both MEDLINE and other PubMed citations may have links to full-text articles or manuscripts in PMC, NCBI Bookshelf, and publishers’ Web sites. If we limit the PubMed search to MeSH controlled vocabulary or the MEDLINE subset, we will see only MEDLINE citations in our results.

10.  References

1. Rogers, Frank B. The Development of MEDLARS. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC198085. Access on 2/1/2014.
2. www.wikipedia.com Access on 2/1/2014.
3. http://www.nlm.nih.gov/pubs/factsheets/factsheets.htmlAccess on 2/1/2014.
4. MEDLINE/PubMed and Other Databases FAQs http://www.nlm.nih.gov/services/journalsbysubject.html Access on 2/1/2014.
5. http://indmed.nic.in/honpaper.pdf