Features - Researching Medical Literature on the InternetBy Gloria Miccioli, Published on May 31, 1998
Gloria Miccioli has been a law librarian for 20 years. Her specialty is research. She has worked as Government Documents/Reference Librarian at the Jacob Burns Law Library of the George Washington University Law School; as Senior Research Librarian for Williams & Connolly; and is currently International Librarian for Jones, Day, Reavis & Pogue's D.C. office, where she provides expert research services for the firm's overseas offices.
After preparing this article, I have become convinced that there are at least as many medical Web sites as there are legal ones, which is good news for the researcher with a small to non-existent medical collection. The Internet provides free access to a great deal of the medical literature, either in full text or citation/abstract format, and it offers search capabilities good enough to fulfill most information needs.
Journals, dictionaries, textbooks, indexes - all can be found on the Net in growing numbers. The sources are varied: publishers, government agencies, professional organizations, and health libraries, to name a few. A simple, if time-consuming, way to find lots of health-related links is to access the Yahoo! search engine and select the category, "Science." Click on "Medicine" and you will pull up almost 100 subcategories, including "Libraries," "Journals," and "Dictionaries." Each subcategory links to various sites, of which some may be useful - or not. Under "Dictionaries" are links to seven medical dictionaries, including one with terms in several European languages. You can also search by subject in an attempt to narrow the number of hits and get the mixed bag that usually results from a Web search on a general search engine.
A more specific approach would be to directly access a medical Web site. But which one? (I am going to discuss selected Web sites. For an excellent, comprehensive introduction to medical research on the WWW, see How to Search for Medical Information, by Frank Kellerman, Mary Zammarellli, and Robert Balliot.) As usual, it depends on what you're looking for. MEDLINE, one of the jewels of medical research, is an electronic index that provides citations/abstracts to some 3900 American and foreign biomedical journals since 1966. As such, it is a mainstay of medical research, especially for current information. It has long been searchable for a fee through commercial databases. It is now available on the World Wide Web. Since it is produced by the National Library of Medicine, a government agency, it is offered at no cost on the Net and is accessible not only from the NLM web site but also from many other sites, such as those of medical libraries, medical associations, and other health-oriented sites.
A list of Web sites where MEDLINE can be searched for free is found at Dr. Felix's Free MEDLINE Page. Dr. Felix provides a handy chart that lists MEDLINE sites with links, plus any registration requirements, usage restrictions, document delivery options, and links to additional information. It is important to note that not all MEDLINE sites are the same. As Dr. Felix says, "...some of these sites only provide free access to certain parts of the vast MEDLINE database. Some permit quite detailed searching, others simple keywords only. Some have usage restrictions..." In fact, MEDLINE is available from the National Library of Medicine in two official versions, Pub Med and Internet Grateful Med. The two Web products are both similar and different.
Internet Grateful Med
Internet Grateful Med (IGM), offers assisted searching of MEDLINE and ten other NLM databases. (There is some overlap among MEDLINE and these other databases, but the more specialized database usually provides greater coverage within a narrower topic. For example, AIDSLINE indexes monographs, scientific reports, and A/V materials as well as articles, but only those dealing with AIDS or HIV.) Each database must be searched separately. Click on the "Search Other Files" button to select. The ten files are:
- PREMEDLINE: Introduced in 1986, it provides basic citations/abstracts before the data is put into MEDLINE. It is updated each weekday with no subject headings or guarantee of quality control. Once the record is added to MEDLINE, iis deleted from PREMEDLINE. PREMEDLINE is free only through IGM or PubMed.
- SDILINE: Selective Dissemination of Information online; covers cites from the most recent complete month in MEDLINE.
- OLDMEDLINE: Covers articles from 1964-65; cites only.
- AIDSLINE: AIDS and related topics, 1980 and after.
- AIDSDRUGS: Directory of substances being tested in AIDS-related clinical trials.
- AIDSTRIALS: Clinical trials of substances being used against AIDS and HIV.
- HealthSTAR: Information on health administration.
- DIRLINE: Directory of information sources.
- HISTLINE: Information on the history of medicine.
- HSRPROJ: Health services research projects in progress.
Internet Grateful Med was designed for the end user; knowledge of a search command language is not necessary. In addition, Grateful Med helps the user find precise medical terminology, i.e., MeSH headings. The National Library of Medicine has developed an extensive controlled vocabulary called Medical Subject Headings (MeSH); using MeSH terms in a search will lead to greater accuracy and relevancy in search results. By entering a term in Grateful Med and then clicking on "Find MeSH/Meta Terms," you can access NLM's Unified Medical Language System's Metathesaurus. Just browse through a ranked list of terms, MeSH hierarchies, and relevant co-terms, then select terms to be added to your search. You can also designate MeSH headings to be "major topics."Terms will also be automatically "exploded"; that is, subheadings of a term will be searched along with the main heading.
The IGM search screen allows users to also search by keyword, author or title words. Limiting by language, age group, study group, date range, publication type, gender, and journal title (searching from one to fifteen journal titles at a time) is possible via pull-down menus. Records can be viewed or downloaded in citation or abstract format. The full-text can be ordered online for a fee from the NLM Loansome Doc delivery system.
Internet Grateful Med strikes me as a good Web product, although it is not as powerful as MEDLINE on Dialog. NLM has put a great deal of effort into making it user-friendly. Having the system present you with relevant MeSH headings allows for better searching than using only key or title words and is very convenient for the searcher who is unfamiliar with medical terminology. The Metathesaurus function itself is somewhat confusing at first. I recommend reading the The New User's Survival Guide and doing a few practice searches.
PubMed is both broader and narrower in scope than Internet Grateful Med. PubMed was developed by the National Center for Biotechnology Information (NCBI) at the National Library of Medicine in conjunction with publishers of medical literature. PubMed not only indexes articles but also links to the full text of journals at the Web sites of participating journals. At present there are links to the full text of about 100 journals (out of some 3,900 indexed by MEDLINE). Access to the full text depends on the publisher; some require a fee or subscription. You can check a list of titles at http://www.ncbi.nlm.nih.gov/PubMed/fulltext.html. Unlike IGM, which accesses 10 databases besides MEDLINE, PubMed covers only MEDLINE and PREMEDLINE, plus links to NCBI's molecular biology databases. However, for a participating journal indexed selectively for MEDLINE, PubMed includes all articles from that journal, even if MEDLINE does not.
PubMed seems to be aimed at the more experienced searcher or health-care worker. Like many Web-based search engines, PubMed offers Basic and Advanced searching. The Basic screen allows keyword searching of subjects, author names, or journal titles. The Advanced search mode is much more sophisticated; the searcher can use either pull down menus or PubMed command language for comprehensive field searching. Fields include author name and affiliation, journal title, issue, volume, publication date, language, text word, title word, substance name, and MeSH headings (headings can be designated "major"), and all fields. (In PubMed, MeSH terms are automatically exploded if the MeSH field is selected; MeSH terms found using an "All Fields" search are not.) The Boolean operators AND, OR, and NOT can also be used. For a complex search, I would choose PubMed over Internet Grateful Med.
PubMed has several ways to lead you to precise medical terminology. It automatically tries to match search terms against a list of recognized phrases. If a match is not found, the individual terms are ANDed together. If that doesn't produce satisfactory results, you can put the phrase in quotes, which tells PubMed to check another dictionary. The user is cautioned to use quotes only as a final option. For either a basic or advanced search, you can click on "MeSH Browser,"enter a term and MedPub will respond with the correct MeSH heading(s), which can then be selected. When I entered "norplant," I got the MeSH heading "levonorgestrel" and a short definition. You can also view the term hierarchy, from which you can select more terms to add to your search. In the Advanced search mode, there is a pull down menu item, "List Terms," which gives you an alphabetical list of terms. This is useful for words you can't spell!
Search results in PubMed are first produced as a Document Summary Page with brief bibliographic information. Documents can be selected to be viewed individually or as a group, and in any of several formats. One of PubMed's most useful features - and a good reason to use this database - allows the searcher to retrieve related articles for most citations. Most PubMed records are linked to other records through a matching algorithm. Once an article is selected, the user can click on "See Related Articles" to get other relevant citations. This is like the "More" feature in Lexis/Nexis. For the full text of the articles, you can link to a participating journal or order online from NLM through Loansome Doc.
PubMed has several other useful features. The Journal Browser lets you look up journal names, MEDLINE abbreviations, or ISSN numbers. The Citation Matcher allows you to verify article citations. A Clinical Query Form is available to search for the therapy, diagnosis, etiology and prognosis of a topic.
I like Internet Grateful Med and PubMed. Although I am used to the familiarity of searching MEDLINE on Dialog and the ease of searching it on Lexis/Nexis, I found the Web versions to be very attractive alternatives. Besides the cost advantage of Web searching, I am impressed by the ways in which NLM has made its MeSH headings available. With IGM and PubMed, it is very simple to find terms that will make up an accurate, comprehensive search. My experience has been that using the correct medical vocabulary is the most important factor when looking for medical information. Further, getting the actual articles has always been a time-consuming process. With the NLM Web products, the user merely has to point and click to order articles, some of which may be online.
However, both systems take a bit of practice. Maneuvering among the MeSH browser, pull-down menus, and various fields - i.e., defining and modifying the query - took time and was hard to keep track of. I couldn't really compare the results of an IGM search to one in PubMed because I couldn't always use the same search in both. For example, PubMed and Grateful Med have divided the date ranges on their pull-down menus differently. Other differences between the two, while giving me more choices, also added to my confusion. I do think that IGM and PubMed are good vehicles with which to search MEDLINE, but I won't throw away my Dialog password just yet.
If MEDLINE is available in not one, but two, formats from NLM, why would a researcher choose to search it on a non-NLM Web site? One reason is convenience, especially if the user is already on another medical site that links to MEDLINE. Often the link is to either PubMed or Grateful Med. A more compelling reason is that some sites offer MEDLINE searching with a little extra added.
Evaluated MEDLINE (I'll call it EM), found on the BioMedNet Website, is an example. BioMedNet calls itself an "online club" that targets the worldwide biological and medical research community. Produced by Electronic Press Limited, EM gets its name from experts' evaluations of articles that appear as links from selected MEDLINE records. EM also links to journals both within and outside of the BioMedNet Library. For a list of the journals within the BioMedNet Library, see http://biomednet.com/library. In addition, there are links from MEDLINE records to journal articles within the BioMedNet collection that cite them.
EM uses Bibliotek2 search software and offers fairly sophisticated searching, including Boolean searching, ordered proximity searching, and field searching. There is also a separate button for searching by MeSH headings. A very useful feature is the ability to combine previous searches and to keep a record of one's search history even after sign-off. A Table of Contents button allows browsing through the tables of contents of any of MEDLINE's journals.
Evaluated MEDLINE search results can be sorted by relevance or date. Full text links to articles, if available, are provided. Hard copy can be ordered online from the British Library Document Supply Center. A researcher may well choose to search Evaluated MEDLINE in order to take advantage of these features.
Infotrieve, a library services company that offers full-service document delivery databases on the Web, also offers FREE MEDLINE with point and click document ordering. The Infotrieve Online search engine allows the user to use either natural language or Boolean logic and field searching via pull-downs or field tags. Like Evaluated MEDLINE, FREE MEDLINE keeps a record of search queries and allows previous queries to be combined.
Another commercial medical Web site with a slightly different take on MEDLINE searching is HealthGate, which provides free searching of MEDLINE and six other databases (AIDSDRUGS, AIDSLINE, AIDSTRIALS, CANCERLIT, and HealthSTAR). Click on "Free MEDLINE" and choose between Basic and Advanced searching. The READER software matches natural language queries to MeSH headings. The Advanced screen accommodates Boolean logic and field restrictions.
HealthGate goes beyond MEDLINE in its coverage of the medical literature, and so do many other medical sites. The HealthGate Data Corp. both provides links to medical reference tools and supplies fulltext reference materials of its own. Some information is free; some is not. For example, through HealthGate, the researcher can link to non-NLM bibliographic databases such as EMBASE, PsycINFO, Age Line, and MDX Digests, but this access is not free.
Full-text, fee-based medical sources on HealthGate include the MDX Family Library (guides to medical tests, drugs, symptoms, et al.) and DIH: Drug Information, among others. Free full-text sources include Diagnostic Procedures, the online equivalent of Diagnostic Procedures Handbook, ed. by Joseph A. Golish. HealthGate publishes medical information as well; its Healthy Living Series is comprised of online articles on various topics and is free. To access both the free and fee-based sources, click on the appropriate button on the home page. HealthGate has several payment plans, including a flat monthly fee and a transactional plan.
MedConnect is another commercial site that provides free MEDLINE as part of its goal to be the "online hub for physicians and other health care professionals." It, too, goes beyond MEDLINE and has published its own medical information on the Web since 1994. MedConnect offers literature reviews, articles, journal clubs, board reviews, and teaching files. Articles written for MedConnect focus on emergency medicine, pediatrics, managed care, and primary care, although coverage of more topics is planned.
Medscape is a "multi-specialty, commercial Web service for clinicians and consumers" that combines information from journals, medical news providers, medical education programs, and materials created for Medscape. Although it offers MEDLINE searching, I couldn't find any sites after 1996. Skip MEDLINE on this site and go instead to Medscape's collection of 7,000 free, full-text, peer-reviewed clinical medicine articles that are searchable and enhanced with navigable tables of contents, zoomable graphics, and links to Internet resources. The Home Page will lead you to information by medical specialty; a group of articles on 21 health and disease topics aimed at the patient; and reference sources such as Drug Search; Drug Interaction Search, Online Medical Dictionary; and the Medscape Bookstore. The latter is a searchable file of health-related textbooks available for purchase online, which would be very useful for identifying texts. Click on the "Site Map" to get an alphabetical list with links of the various resources on Medscape.
A recent two part article on Medscape by Stephen E. Smith entitled Medical Search Engines - Myth or Marvel is a useful resource on medical search engines. Using the search page, www.medscape.com/Home/Search/formMedscape.html, enter the phrase "medical search engines" in the query box. In these articles Mr. Smith reviews different medical search engines and medical metasites. It's also a good place to find the names of some individual sites. Part II discusses more metasites. Another list, with links, of 14 medical metasites and search engines can be found at www.dml.georgetown.edu/hsintresources.html. Click on "Health Sciences Search Engines and Directories."
If you need a comprehensive guide to clinical medicine resources on the Internet, run, don't walk, to Medical Matrix. This metasite annotates, evaluates and links to medical sites that "are relevant to the clinical practice of medicine, interesting to a general population, and easy to retrieve." An editorial board reviews and ranks all resources. For example, if you click on the "MEDLINE" button, you will see that Medical Matrix has links to over 10 MEDLINE sites, including Internet Grateful Med, PubMed and Evaluated MEDLINE. It also briefly describes each site and links to a very handy comparison chart. In addition the sites are ranked by a rating system of stars. PubMed has the highest rating, 5 stars. Rankings are explained at www.medmatrix.org/info/about.html.
To get an idea of the breadth of coverage available on Medical Matrix, I entered "panic disorder" in the Home Page search box. I got only two hits, but I was given a broader heading, "Psychiatry: Diseases - Anxiety". I clicked on it and was rewarded with a list of over 50 sites that were grouped by type of information. Each listing was linked to a specific web site; each listing was ranked. A rundown of categories that were retrieved follows: news articles (from medical and nonmedical sources), medical articles, reports of professional meetings and conferences, organizational resources (e.g., American Psychological Association's APA Online), reference documents such as Psychiatric Medication Fact Sheets, the World Wide Web Psychotherapy Guide, decision tools (Mood Disorder Diagnostic Program), practice guidelines, mental health cases and teaching files on the Web, textbooks, online forums, patient education materials, and, of course, MEDLINE.
Users can also select to search the resources within a specialty or category found on the Home Page. For instance, clicking on "Rx Assist" brings up links to 27 online drug resources, including the PDR Online Drug Database. Medical Matrix provides the kind of one-stop shopping and searching that we see in FindLaw and LawCrawler.
Hospitals, medical libraries, and professional associations that have a presence on the Web often provide links to sites that reproduce or index medical literature. In addition, the online catalogs of medical libraries are a window to the world of medical publishing. Medical/Health Sciences Libraries on the Web links to academic, hospital, and military medical libraries. MedWeb, the medical metasite of Emory University's Health Sciences Library, is impressive for its links to health-related sites located around the
" world. For example, I clicked on "Israel" in the Country Index, then "City of Haifa," and got a list of links to medical web sites in that city, including hospitals, medical centers, and medical schools. Select a broad category on the home page, such as "Dentistry," and you will get links to dentistry-related sites worldwide. My attempt at a subject search of the entire site, however, was not successful. I tried "panic disorder," "anxiety" and "phobia" and got no hits.
HealthWeb, is the result of a group effort of the health sciences libraries of the Greater Midwest Region, the National Network of Libraries of Medicine, and those of the Committee for Institutional Cooperation. It is designed to provide "access to evaluated non-commercial, health-related, Internet-accessible resources." I clicked on the "Subjects" button and got a list by subject specialty; clicking on "Psychiatry" yielded links to 11 web sites plus brief annotations of each site. Searching can also be done by keyword.
Finally, the research of medical sources is often a hunt for visual information. The fact that the Internet is not restricted to textual information makes it an extremely valuable research tool. The MedBot search engine groups its sites by type of information. An interesting selection is "Medical Images and Multimedia," which allows you to search for graphics. I entered "keratosis," which is a skin lesion, in the search box and retrieved several hits that linked to images. There is also a separate box to search the "Digital Anatomist," a collection of computer-generated images of the brain, thoracic organs, and the knee.
The Internet has become an important source of information in medicine and the health sciences, as it has in so many other areas. Information professionals are at the forefront of the effort to organize this vast, ever-increasing store of knowledge. The sites mentioned above reflect this effort and are meant to be a sampling of the marvelous tools that are now available to the medical researcher. Take some time to explore medicine on the Web; no doubt you'll discover many more.
Dr. Felix's Free MEDLINE Page
A list of Web sites where MEDLINE can be searched for free Internet Grateful Med (IGM)
offers assisted searching of MEDLINE and ten other NLM databases PubMed
indexes articles; also links to the full text of journals at the Web sites of participating journals Evaluated MEDLINE
"online club" that targets the worldwide biological and medical research community FREE MEDLINE
point and click document ordering HealthGate
provides links to medical reference tools and supplies fulltext reference materials MedConnect
offers literature reviews, articles, journal clubs, board reviews, and teaching files
collection of 7,000 free, full-text, peer-reviewed clinical medicine articles that are searchable Medical Matrix
this metasite annotates, evaluates and provides links to medical sites HealthWeb
access to evaluated non-commercial, health-related, Internet-accessible resources MedWeb
medical metasite of Emory University's Health Sciences Library