NLM Gateway

NLM Gateway, a Web-based metasearch engine for many resources of the National Library of Medicine (NLM), searches MEDLINE/PubMed, the NLM Catalog, TOXLINE Special, Developmental and Reproductive Toxicology (DART), Meeting Abstracts (HIV/AIDS, Health Services Research, and Space Life Sciences), five subfiles of the MedlinePlus consumer health database, ClinicalTrials.gov, DIRLINE, Genetics Home Reference, Health Services Research Projects (HSRProj), Online Mendelian Inheritance in Man (OMIM), and five toxicology databases (HSDB, IRIS, ITER, GENE-TOX, and CCRIS). Developed by the library's Lister Hill National Center for Biomedical Communications, the Gateway debuted in October 2000 as part of the migration from the older ELHILL fee-based search system to free access on the Web [1].

The target audience for the Gateway is “the Internet user who comes to NLM not knowing exactly what is here, or how best to search for it” [2]. The Gateway is best understood as “first-stop shopping” [3] for some of the gems in the NLM's collections of resources. Its twenty separate systems are grouped visually into three collections appropriate for users from a wide variety of subject specialties and educational levels: Bibliographic Resources, Consumer Health Resources, and Other Information Resources. Each constituent database (there are now 20) has a link to its own separate interface, except for Meeting Abstracts, which may be accessed only through the Gateway or through an Internet search engine such as Google.

The clean design of the home page features a single search box (Figure 1); users may enter their own terms or click Term Finder to find indexing terms from Medical Subject Headings (MeSH) or Unified Medical Language System (UMLS). Boolean operators, field qualifiers, and several limiters may be used (these are ignored for collections that do not support them). The user may view Search Details explaining how terms are searched in each database; History displays previous search statements; and the user may choose a password to store settings or references in a Locker. The number of search results is displayed for each constituent database; clicking the number or database name displays the list of results. The Gateway is exceptionally easy to navigate; clear directions at each step explain what to do next.

Figure 1.

NLM Gateway search screen

As might be expected from such a disparate collection, the Gateway is more successful at handling certain types of queries. For example, the MeSH term “Rotavirus Infections” produces a reasonably precise set of references in each of several subfiles. However, phrases such as “mosquito control” or strings of common words such as “vitamin c aged common cold” (an example from the NLM Training Manual) [4] produce large numbers of apparently irrelevant references, especially in the Consumer Health collection, because Gateway “cannot duplicate exactly the processing sequences and capabilities of each [system]” [5]. Phrases and limits are not recognized by some collections. Using Search Details, one may view, but not change, the way queries are parsed in each system.

Another problem is the layout of the Gateway home page, which first lists MEDLINE/PubMed references (many of which are written at a postgraduate level incomprehensible to the average person). To answer general consumer health questions, going directly to MedlinePlus seems preferable. Use of a search wizard or better clustering of systems by user category or subject might improve usability of the Gateway for the nonspecialist. Also, the inexperienced user may not realize that the Gateway does not search all NLM resources (more are found on the NLM Website) and is not a US government-wide search engine.

In summary, NLM Gateway, like its largest constituent database, PubMed, “can provide more depth but may require more effort to use; training may help searchers to obtain the best results” [6]. Consumers use a wide variety of Web-based health resources [7] and might not wish to expend the effort to learn a complex system. NLM's Gateway Basics trifold brochure is recommended for a brief overview. In spite of its wealth of resources, the Gateway seems to have limited appeal to the new generation of users who expect to connect immediately to a custom-tailored display of full-text results. Usage statistics have slipped from a high of 1.6 million in fiscal year 2002 to 722,000 in fiscal year 2005 [8], despite skyrocketing use of the Web. Today's searcher apparently prefers other search engines such as PubMed, Google, Google Scholar, and HighWire Press (which now has a PubMed search option) [9].

The lack of references to the Gateway in CINAHL nursing journals suggests that this resource is little used by nurses, although a PubMed search for “NLM Gateway” finds the Gateway mentioned in several Cochrane reviews, as a key resource for health sciences librarians [10], public health professionals [11], and physician writers [12]. Whether or not the Gateway is used as a search engine, it is still valuable as a collection of world-class resources and, as such, deserves a place on the Website of every sizable library serving health sciences users. Perhaps it can be reengineered to serve a wider audience of twenty-first century users as capably as the ELHILL system served an earlier generation of health sciences librarians.