A typical MEDLINE file contains the following information:
- UNIQUE IDENTIFIER: This number is assignged by the National
Library of Medicine.
- AUTHOR: There are often multiple authors.
- TITLE: Indicates the title of the article.
- LANGUAGE: Indicates the language the article was published
in.
- MESH HEADING: This stands for "medical subject heading."
The National Library of Medicine organizes articles according
to a list of medical subject headings, otherwise known
as key words.
- PUBLICATION TYPE: Indicates whether the publication
is an article, a comment letter, or a review article.
- NUMBER REFS: Indicates how many articles are referenced
by the selected article.
- ABSTRACT: This is a summary of the article. You will
need to obtain the complete article from the cited journal.
- SOURCE: Indicates the journal in which the article was
published.
Does MEDLINE include all medical journals? No. The decision
whether or not to include a journal for MEDLINE is made
by the Director of the National Library of Medicine, based
on considerations of both scientific policy and scientific
quality. The Board of Regents of the Library sets policy
for the Library.
The Literature Selection Technical Review Committee (LSTRC)
has been established to review journal titles and assess
the quality of their contents. The LSTRC frequently incorporates
the review and advice of outside experts in the subject
area. As a result of these reviews, currently indexed titles
may be dropped and new titles added. As of October, 1995,
3147 journals were indexed in Index Medicus. The LSTRC meets
three times a year and considers approximately 120 titles
at each meeting. Additional titles are considered in reviews
of specialty coverage, but the selection is highly dependent
on the judgment of Committee members and the Director.
The following critical elements are intended as a general
guide so that a consistent set of issues will be considered
as the Committee members examine journals in their search
for the best and the most appropriate coverage of the biomedical
literature.
Critical Elements
Scope and coverage: Index Medicus and MEDLINE provide
access to the biomedical literature. The journals brought
to the Committee for review will contain articles predominantly
on core biomedical subjects. Journals whose content is predominantly
a subject peripheral or related to biomedicine are occasionally
brought to the Committee when they have some biomedical
content. In these cases, the Committee's advice is sought
not only on the quality of the content but also on the contribution
it makes to the coverage of the subjects in question. Generally,
such journals will not be indexed if their biomedical content
is already adequately covered.
Quality of content: The scientific merit of a journal's
content is the primary consideration in selecting journals
for indexing. The validity, importance, originality, and
contribution to the coverage of the field of the overall
contents of each title are the key factors to be considered
in recommending a title for indexing, whatever the intended
purpose and audience.
Quality of editorial work: The journal should demonstrate
features that contribute to the objectivity, credibility,
and quality of the contents. These features may include
information about the methods of selecting articles, especially
on the explicit process of external peer review; timely
correction of errata; explicit responsible retractions as
appropriate; and opportunity for comments and dissenting
opinion. Neither the advertising content nor commercial
sponsorship should raise questions about the objectivity
of the published material. Sponsorship by national or international
professional societies may be considered.
Production quality: The quality of the layout,
printing, graphics, and illustrations are all considered
in assessing a journal. Though not a requirement for selection,
journals destined to be of archival importance should be
printed on acid-free paper.
Audience: MEDLINE and Index Medicus are intended
primarily for all those in the health professions: researchers,
practitioners, educators, administrators, and students.
The phrase health professionals includes physicians, nurses,
dentists, veterinarians, and the many types of allied health
professionals in the research and health care delivery systems.
Types of content: Journals whose contents consist
of one or more of the following types of information will
be considered for indexing:
- Reprints of original research
- Original clinical observations accompanied by analysis
and discussion
- Analysis of philosophical, ethical, or social aspects
of the health professions or biomedical sciences
- Critical reviews
- Statistical compilations
- Descriptions of evaluation of methods or procedures
- Case reports with discussions
All of these forms of information should be included in
Index Medicus and MEDLINE in order to fulfill the needs
of users. However, coverage of a field tends to create a
priority approximately parallel to the order in which the
types are listed. For example, journals reporting original
research are more likely to contain unique contributions
to the coverage of a field and therefore are selected more
often than those that contain only case reports.
Publications that consist primarily of reprinted articles,
reports of association activities, abstracts of the literature,
news items or book reviews, will not usually be indexed.
Foreign language journals: The criteria for selecting
journals written in a foreign language are the same as for
those written in English. Other things being equal, additional
consideration will be given to the availability of adequate
English- language abstracts that extend the accessibility
of the content to a broader audience.
Geographic coverage: The highest quality and most
useful journals are selected without regard for the place
of publication. In order to provide broad international
coverage, special attention is given to research, public
health, epidemiology, standards of health care, and indigenous
diseases. Journals will generally not be selected for indexing
if the contents are subjects already well represented in
Index Medicus and MEDLINE or that are being published for
a local audience. The interpretation of these criteria will
be influenced by the stated purpose of the journal. For
purposes of illustration, four broad categories of journals
are suggested.
Research journals are predominantly devoted to reporting
original investigations in the biomedical and health sciences,
including research in the basic sciences; clinical trials
of therapeutic agents; effectiveness of diagnostic or therapeutic
techniques; or studies relating to the behavioral, epidemiological,
or educational aspects of medicine.
Clinical or practice journals have as their dominant purpose
documenting the state of current practice, providing background
for those in training, or the continuing education of practitioners.
This is done through the publication of case reports, discussions
and illustrations of new techniques, evaluations of current
practices, and commentaries.
Review journals contain the current state of knowledge
or practice, integrating recent advances with accepted principles
and practice, or summarizing and analyzing the consensus
view of controversial issues in knowledge or practice. Review
journals provide background information for practitioners
and researchers, students and house officers, and others
who wish an overview on the current status of a field.
General or all-purpose journals contain elements of all
the foregoing and frequently contain commentary and analysis
of important social, political, and economic issues. They
are usually designed for a broad audience and not limited
to a specialty.
Questions about the journal selection process and LSTRC
may be answered in "Response to Inquiries About Journal
Selection for Indexing at NLM" or directed to:
LSTRC Scientific Review Administrator
National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894
(301) 496-6921
According to the National Library of Medicine, MEDLINE
and its backfiles contain the following number of citations
as of December 1996:
| Database |
Years Covered |
# of Citations |
% in English |
% with Abstracts |
| MEDLINE |
1994 - 1997 |
957,686 |
87 |
72 |
| MED90 |
1990 - 1993 |
1,511,545 |
82 |
74 |
| MED85 |
1985 - 1989 |
1,688,748 |
77 |
62 |
| MED80 |
1980 - 1984 |
1,388,923 |
74 |
51 |
| MED75 |
1975 - 1979 |
1,279,078 |
69 |
41 |
| MED66 |
1966 - 1974 |
1,986,476 |
59 |
0 |
| PREMEDLINE |
most recent |
141,659 |
90 |
79 |
| OLDMEDLINE |
pre 1966 |
307,336 |
53 |
0 |
