sciences libraries in the United States. The relative scale of this funding is underscored by noting that NLM’s total budget in 1964, just before the MLAA funding program began, was only $4 million. MLAA funds were used for the construction and renovation of health sciences libraries, for the acquisition of key resources by health sciences libraries, training in health sciences librarianship, and research and development projects related to health sciences information. Approximately 12% of MLAA funds expended between 1965 and 1970 were also used for the development of NLM’s RMLs.
The first library serving as an RML was the Countway Library at Harvard University, beginning in 1967 (Cummings and Corning, 1971).
Resource sharing was among the principal motivating factors leading to the development of the RMLs. With large health sciences libraries serving as RMLs in what were originally 11 regions, NLM was able to reduce its interlibrary loan activities to fulfilling requests for materials not available from other libraries in the network. Before the RML program began in 1967 NLM fulfilled approximately 175,000 interlibrary loan requests annually.
Three years later, with the first RMLs beginning their service, this fell to approximately 100,000 requests per year. In addition to interlibrary loan service, the RMLs served as MEDLARS search centers and provided reference, consultation and training for health professionals and librarians in their re- gions (Cummings and Corning, 1971). A total of 11 institutions served as RMLs until 1982 when the number of regions was reduced to seven (Bunting, 1987). The number of regions subsequently increased to eight with the separation of the New England Region and the Middle Atlantic Region.
The dramatic increase in funding available to health sciences libraries with MLAA was echoed in the late 1990s with the doubling of the National Institutes of Health (NIH) budget (Brainard et al., 2001). This increase in funding supported NLM’s expansion of its mission to include service beyond health professionals and health sciences libraries to include the general public (National Library of Medicine, 1999).
Several factual databases, including the TOXNET (Toxicology Data Net- work) family of databases, emerged as a result of what was originally known as the Toxicology Information Program at NLM. Through the 1980s access to these databases was available primarily through mediated searches per- formed by library personnel who had access to online accounts and who were familiar with online command languages. Systems that supported searching directly by end users appeared in the 1980s, with librarians adopting the roles of trainer and expert searcher.
With the growth in the size of bibliographic databases, the importance of limiting search retrieval became critical. Search ‘‘hedges’’ or filters emerged as key tools for effective searches, reflected in the ‘‘clinical queries’’
and other filters available today in NLM’s PubMed system. The wide array of often conflicting information available also led to the need for systematic reviews and practice guidelines to support evidence-based decisions. Al- though its principles were not new, the phrase ‘‘evidence-based medicine’’
made its first appearance in the literature in 1992 with an article by Guyatt and other members of the ‘‘Evidence-Based Medicine Working Group’’ at McMaster University (Guyatt et al., 1992). The development of the World Wide Web in the 1990s led NLM to recognize the need to assist the general public in evaluating the plethora of health information available online. This led to the development of MedlinePlus which premiered in October 1998 and which continues to evolve, as noted below, with the addition of infor- mation about health services available in local communities across the United States.
A. Bibliographic Databases
Bibliographic databases have grown tremendously with the burgeoning amount of life sciences literature published since the databases came online in the early 1970s. The flagship databases in health care remain MEDLINE and EMBASE. BIOSIS remains an essential resource for preclinical research and drug development. CINAHL is a welcome addition, focusing on the literatures of nursing and allied health. A variety of approaches to indexing have been used, with significant developments in the controlled vocabularies used to index EMBASE and BIOSIS records.
With a name signifying ‘‘MEDLARS online,’’ MEDLINE became avail- able for online interactive searches in October 1971. As noted previously, MEDLINE extended the success of the MEDLARS system which was orig- inally developed to automate the production of the printed Index Medicus.
Since it first appeared, MEDLINE has grown significantly in size as well as numbers of searches and users. When it came online in 1971, MEDLINE
consisted of just over one million records from the indexing of approximately 2200 journals. It now includes more than 14 million records of articles from more than 4800 biomedical journal titles. MEDLINE includes records of publications from roughly 1966 to the present, with more than half a mil- lion records now added annually.
The growth in the number of MEDLINE users and searches may be attributed to improvements in its ease of access. Through most of its first three decades, MEDLINE was only available online through payment of a nominal fee. Initial access was through searches performed through the use of TWX network terminals. Distributed access to MEDLINE was significantly influenced by the work of Irwin Piser and others at the SUNY, who had demonstrated the proof-of-concept for distributed access to MEDLARS data through terminals in four cities: Albany, Buffalo, Rochester and Syracuse.
SUNY’s distributed access system began in December 1968 and laid the groundwork for expanded efforts by NLM’s Lister Hill Center for Biomedical Communications (McCarn, 1970).
Direct online searches of MEDLINE by end users became possible in 1986 with the release of the Grateful Med software, developed by NLM’s Lister Hill Center for Biomedical Communications. Also in the 1980s CD-ROM sub- scriptions to MEDLINE first appeared. At the time these were released, there were significant concerns in the health sciences library community related to NLM’s providing direct access to its databases for health professionals and other end users. Responses to the release of Grateful Med included a concern that NLM had not articulated the value of hospital and other health sciences librarians as expert searches, complementing the searches that could be per- formed by end users (Humphreys, 2002;White, 1991).
A significant milestone in MEDLINE’s history occurred on June 26, 1997 when NLM made it available free of charge through Internet interfaces.
In 1996 NLM had launched a Web-based version of its Grateful Med soft- ware. Earlier in 1997 the National Center for Biotechnology Information (NCBI), a component of NLM, had released PubMed, a bibliographic com- ponent of its Entrez system which also includes protein and gene sequence databases. A notable feature of PubMed is its use of automatic term map- ping, which relies on the Unified Medical Language System (UMLS) to support free-text searches.
Searches of MEDLINE in 1996 through Internet Grateful Med were performed at a rate of approximately 600,000 per year (Garnett, 1996). With the availability of free searches and the release of PubMed the following year, the number of searches increased more than 10-fold to seven million per year (Zipser, 1998). Today more than 600 million searches are performed in PubMed/MEDLINE each year, a remarkable increase from the 22,000
searches executed in the MEDLARS system in 1970 (Cummings and Corning, 1971; Steinbrook, 2006).
In December 2004 NLM terminated the printing of Index Medicus, which had been published for 125 years. The number of subscribers to this resource had fallen to 155 in 2003 (National Library of Medicine, 2004). The termination of the printedIndex Medicusand the steady growth of PubMed/
MEDLINE searches fulfilled the transformation, begun four decades earlier, in the methods used to disseminate bibliographic information in the health sciences. This transformation continues with the conversion of historic printed materials into Internet-accessible electronic resources.
The importance of access to the older literature was underscored with the death in June 2001 of Ellen Roche, a healthy 24-year-old volunteer in an NIH-sponsored clinical trial at Johns Hopkins University. Ms. Roche had volunteered to take part in a study of the pathophysiology of asthma. In order to provoke a mild asthma attack, the healthy participants in this study inhaled hexamethonium, a drug that had been used as an antihypertensive agent in the 1950s and 1960s. Following her inhalation of hexamethonium Ms. Roche developed a cough, and her condition deteriorated until her death approx- imately 1 month after entering the study. The federal Office for Human Research Protections (OHRP) investigated the study and 6 weeks following the death of Ms. Roche suspended all federally sponsored research projects at Johns Hopkins and affiliated institutions. The suspension was lifted after quick corrective action was taken by the university. The central concern in the hexamethonium study was the failure to uncover reports of its toxicity avail- able in the journal literature from the 1950s (Savulescu and Spriggs, 2002).
Online access to records of biomedical journal articles published from 1950 to 1965 is now available through NLM’s OLDMEDLINE database, accessible as part of the PubMed system. OLDMEDLINE includes approx- imately 1,760,000 records and complements the MEDLINE database, which provides records published inIndex Medicus from 1966 onward.
Begun in 1947 as a set of eight ‘‘abstract journals’’ through a collab- oration of three Dutch physicians,Excerpta Medicanow indexes the literature in 42 medical specialties. EMBASE, the electronic equivalent of Excerpta Medica, came online through Dialog in 1974. Two years previously it had been acquired by Elsevier. EMBASE now has more than 10 million records and serves as an important index of the biomedical literature, with partic- ularly strong coverage of pharmacology and the European literature. The majority of EMBASE records are of journal articles, but 5% are records of conference proceedings, technical reports and monographs (Dialog, 2005a).
A study in 1991 found that 51% of EMBASE titles are also indexed in
MEDLINE, underscoring the importance of searching both databases if comprehensive coverage is needed (Mychko-Megrin, 1991).
In 1991 EMBASE introduced the EMTREE Thesaurus as its control- led vocabulary. Previously, the Master List of Medical Indexing Terms (MALI- MET) had been used (Boorkman et al., 2004). The EMTREE Thesaurus in- cludes approximately 46,000 ‘‘preferred’’ terms as well as close to 200,000
‘‘synonyms,’’ including proprietary drug names, MeSH terms and obsolete EMTREE terms. Somewhat comparable to MeSH subheadings, EMTREE terms can be qualified with ‘‘drug links’’ or ‘‘disease links’’ (Dialog, 2005a).
Originally a non-profit organization founded in 1926 but acquired by Thomson in January 2004, BIOSIS is headquartered in Philadelphia. The BIOSIS Previews database is the electronic equivalent of the printedBiological Abstracts and Biological Abstracts/Reports, Reviews and Meetings, with coverage dating from 1969. Today BIOSIS Previews includes more than 14 million records, including records of articles indexed from more than 5000 journal titles. Other publication types represented include conference papers, mon- ographs and US patents (Dialog, 2005b). With broad coverage of the life sciences, BIOSIS Previews is routinely used in health sciences settings for research related to environmental health, preclinical sciences and drug de- velopment.
BIOSIS makes its Vocabulary Guide available as part of the larger BIOSIS Search Guide. The Vocabulary Guide lists approximately 20,000 ‘‘key terms’’ selected on the basis of their frequency in the database. Since 1993 BIOSIS has relied on ‘‘relational indexing’’ which uses links as qualifying concepts. BIOSIS Previews searchers may also take advantage of the data- base’s 168 ‘‘major concepts,’’ which can be exploded to retrieve more specific concepts. The Vocabulary Guide also includes concepts codes and biosys- tematic codes (BIOSIS, 2002).
The Cumulative Index to Nursing and Allied Health Literature was originally published from 1956 to 1976 as the Cumulative Index to Nursing Literature. In 2003 it was acquired by EBSCO Publishing. Its electronic equivalent, the CINAHL database, covers the Nursing and Allied Health Literature since 1982, with over one million records of journal articles as well as conference papers, nursing dissertations, books and educational software.
CINAHL indexes roughly 1600 journal titles. The database also includes more than 22,000 full-text records of articles from selected-state nursing journals as well as newsletter articles, research instruments and government publications. Indexing of CINAHL records relies on the set of almost 12,000 CINAHL subject headings, approximately 70% of which are also MeSH terms. Like MeSH, CINAHL subject headings are updated annually, are
hierarchically organized with broader terms that can be exploded, and may be qualified with subheadings (CINAHL, 2005).
B. Systematic Reviews and Other EBM Resources
The idea that clinical decisions should be made on the basis of the best available evidence is not new. This simple principle is at the heart of what has become known as the evidence-based medicine (EBM) movement. With origins at McMaster University in the early 1990s, EBM was hailed inNew York Timesmagazine in 2001 as one of the most influential ideas of the year (Haynes, 2002). EBM has spawned parallel frameworks in other disciplines, including evidence-based nursing, evidence-based public health and evi- dence-based librarianship. The emphasis in all evidence-based movements is on making decisions that are consistent with the best evidence available, rather than primarily on a practitioner’s personal experience.
In the face of what can be an unmanageable amount of often contra- dictory information in the literature, EBM proponents suggest a five-step process for reaching clinical decisions that are based on the best evidence available:
1.Define the question. The first step in the practice of EBM is to articulate a clinically oriented, focused question. Such a question includes data about the patient or population, an intervention or exposure, measurable outcomes and, optionally, a comparison (Richardson et al., 1995).
2. Collect the evidence. The second step is to search for relevant evidence, typically through searches of knowledge-based resources such as bibli- ographic databases. PubMed provides a set of ‘‘clinical queries’’ that allow searchers to enter concepts and apply quality filters to retrieve records of controlled clinical trials and other rigorously designed studies.
Other bibliographic resources that may be searched as part of gathering evidence include databases of systematic reviews, such as the Cochrane Library described below.
3. Evaluate the evidence. Critical appraisal of the gathered evidence is the next step, with attention given to the strength of the research design used in the reported studies. The relative strength of various study designs has been depicted as a pyramid with in vitro and animal studies toward the base and randomized-controlled trials and systematic reviews at the apex. Levels of evidence can also be based on guidelines such as those provided by the US Preventive Services Task Force (Harris et al., 2001):
I Evidence from a minimum of one randomized-controlled trial.
II-1 Evidence from controlled trials that were well designed but did not include randomization.
II-2 Evidence from cohort- or case-control analytic studies.
II-3 Evidence obtained from comparisons made between times or places with or without the intervention.
III Opinions of respected experts.
4. Integrate the evidence with patient- or community-specific data to reach de- cisions. Consideration of patient-specific data and the integration of this data with the previously gathered and evaluated evidence constitute the fourth step in the EBM framework. Patient-specific data may include the patient’s clinical condition as well as other factors such as her history, preferences related to care and spiritual beliefs. Practitioners of evidence- based public health may integrate evidence with population-specific data to reach a decision impacting a particular community.
5. Review the process for possible improvements. The final step entails reflect- ing on the process in terms of identifying opportunities for improving its practice in the future. These opportunities may relate to resources and methods for searching the available evidence, domains in which health sciences librarians possess expertise (Guyatt and Rennie, 2001).
Critics of EBM note that it is often impractical and may not be cost- effective to delay clinical decisions until the best available evidence can be retrieved, evaluated and integrated with patient-specific data. Others note that EBM devalues a clinician’s personal experience, and that decisions rou- tinely must be made in the absence of evidence. Newly emergent problems, such as the SARS (severe acute respiratory syndrome) epidemic of 2003, require decisions in the absence of previous relevant research. Finally, many routine clinical practices such as blood transfusions have not been the subject of randomized-controlled clinical trials due to ethical concerns related to withholding treatment (Timmermans and Mauck, 2005).
EBM has gained wide acceptance over the past two decades, and a host of new information resources have emerged to support its practice. Chief among these are systematic reviews, publications that focus on specific clinical problems and that integrate findings from multiple primary sources. Unlike traditional narrative reviews of the literature, systematic reviews provide specific criteria for how primary studies are identified and evaluated. Meta- analyses are a type of systematic review that pool data from multiple primary sources with the intent of performing new analyses of the aggregated data.
Archie Cochrane (1909–1988), a Scottish epidemiologist, pointed to the need for systematic reviews with the observation that, ‘‘It is surely a great
criticism of our profession that we have not organized a critical summary, by specialty or subspecialty, adapted periodically, of all relevant randomized controlled trials’’ (Cochrane, 1979). Cochrane’s 1972 book, Effectiveness and Efficiency: Random Reflections on Health Services, underscored the importance of randomized-controlled trials in evaluating the effectiveness of treatments and called for an international registry of trials.
Established in Oxford in 1993, 5 years after Cochrane’s death, the Cochrane Collaboration (www.cochrane.org) is now an international, coor- dinated effort to generate and disseminate systematic reviews. Divided into more than 40 review groups, participants in the Cochrane Collaboration work together to identify randomized-controlled trials and to create records in the Cochrane Controlled Trials Register. Participants in review groups also evaluate the results of studies on the basis of evidence-based criteria and synthesize the findings in systematic reviews. The full text of these reviews is made available through the Cochrane Database of Systematic Reviews, the principal product of the Cochrane Collaboration.
Practice guidelines are now commonly developed and used with the intent of improving the quality and consistency of care, balancing costs and outcomes and ensuring legal protection. Like systematic reviews, practice guidelines may be evidence based. While many guidelines are based solely on the consensus of experts, evidence-based practice guidelines rely on a sys- tematic search of the available evidence and an evaluation of the strength of the evidence. The specific recommendations included in an evidence-based practice guidelines are weighted on the basis of the strength of their sup- porting evidence. Although they have been criticized as ‘‘cookie-cutter’’
medicine, practice guidelines have been produced by government agencies, professional associations, health care organizations and disease-specific ad- vocacy groups (Wilsonet al., 1995). NLM maintains a collection of full-text guidelines as part of the PubMed ‘‘Bookshelf’’ (www.ncbi.nlm.nih.gov/
books/bv.fcgi?rid=hstat), and the Agency for Healthcare Research and Qual- ity (AHRQ) sponsors the National Guideline Clearinghouse at http://
guidelines.gov.
C. Factual Databases
A host of databases provide factual information in the health sciences, key resources for health sciences librarians in addition to bibliographic databases.
Databases of toxicology and environmental health information developed at NLM as part of its Specialized Information Services (SIS) division were among the first factual biomedical databases to become available online.
Today other factual databases are available that provide information about