In April, Elsevier will release a combined search engine and database to help clinicians diagnose and treat a variety of disorders. ClinicalKey, now in beta testing, offers access to all of Elsevier's clinical journals and textbooks, along with a search engine that can do some interesting tricks I've not seen before.

The company recently gave me access to their beta site, so I decided to do an A/B comparison with Wolters Kluwer's UpToDate, one of the most well-respected search engines in medicine.

Both search engines boast a huge collection of resources. ClinicalKey taps into Elsevier's impressive medical library, offering full-text access to over 400 of its journals, 700 books, and 2,500 procedural videos. Unfortunately, you can't get full text access to journals that Elsevier doesn't publish, including some of the most important ones like the Journal of the American Medical Association and the New England Journal of Medicine.

UpToDate approaches medical education differently. Rather than offering readers direct access to journals and textbooks, its database consists of original reviews of the medical literature written by more than 4,800 experts with whom they contract. The reviews cover over 9,000 topics, spanning about 97,000 pages of text in 19 specialties.

The difference in the two companies' approaches is worth a closer look. UpToDate's strength is the fact that its expert authors look at all the research in the journals and then synthesize it into focused reviews that sum up the most useful approach to diagnosis and treatment.

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ClinicalKey, on the other hand, offers the more comprehensive approach by providing a mountain of journal articles and textbook chapters that the end user can choose from. The downside to having to wade through all this data, of course, is the doctor has to decide which journal articles and book chapters to read and who the most authoritative experts are.

However, ClinicalKey offers an alternative that directly competes with UpToDate. Readers have the option of clicking on the "First Consult" filter, which calls up an original review of the medical literature on the topic by subject matter experts.

One of the features that UpToDate touts is the timeliness of its reviews. For instance, a review on hyperthyroidism that I just looked at (February 2012) was last updated by their experts in November. That's pretty current.

At the top of the list of references in my ClinicalKey search on hyperthyroidism was Current Surgical Therapy, Tenth Edition, which may have been published in 2011 but certainly wasn't written in November. In fact, one of the complaints about the long lead time for the publication of textbooks is that they are often out of date by the time they're published.

The first journal reference was dated 2011 but was a case report, which is usually not as useful to a doctor at the point of care as a topic review—unless, of course, his patient's presentation is similar to the patient in the case study. However, if you look at ClinicalKey's First Consult reviews, the first article on hyperthyroidism is dated June, so they're neck-and-neck with UpToDate.

One advantage ClinicalKey offers that impressed me is its "smart content," an exhaustive collection of medical taxonomy tags that provides end users with more than the traditional predictive search capability seen in UpToDate.

As you type the term hyperthyroidism into UpToDate, you get a drop-down menu suggesting related keywords, including "hyperthyroidism in pregnancy" and "hyperthyroidism symptoms." In total, 10 search terms appear. But when you put hyperthyroidism into ClinicalKey, you get 20 options in the drop-down menu, including "serum T3 measurement", a diagnostic test for the disease, and "iopanoic acid", a drug used to treat the disorder. It's already thinking for the clinician, essentially asking if he or she wants more information on specific aspects of patient care.

ClinicalKey also has better filtering tools. Typing the term hyperthyroidism in UpToDate, I'm given the option of filtering the topic results in only four ways. I can see content on adults, children, patient--which includes patient education material--and graphics. Elsevier offers far more options.

In ClinicalKey, I can choose to look at references from textbooks, journals, First Consult, clinical guidelines, clinical trials, or images, or I can go to Medline, which provides a bibliography of relevant articles. I can also filter the search results by medical specialty or the time period in which the references were published.

Clearly UptoDate now has a major competitor to contend with. Not only does ClinicalKey provide up-to-date expert reviews, it serves up a huge collection of top-notch journal and textbook chapters for physicians who have the time and inclination to dig deeper. Plus it has a longer list of tags and filters. I can't wait to see what Wolters Kluwer comes back with to stay on top.

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