Clinical decision support programs have been reported to be valuable aids in diagnosing difficult cases.3
Hoffer reported using a clinical decision support program to make the diagnosis of Addison's disease expeditiously when it was missed by many expert clinicians.4
We think that Google is likely to be a useful aid in diagnosis too. It has the advantage of being easier to use and is freely available on the internet.
A few limitations of this study should be mentioned. Arguably, everything could be found on the web if only one knew the correct search terms. In this case, we chose combination of search terms that we felt would be unique (see extra table on bmj.com). We chose between three to five search terms for each case, depending on symptoms and signs that we felt would not return a non-specific result. We selected “statistically improbable phrases” whenever possible,6
such as “cardiac arrest sleep” in case record 37. We generally selected likely diagnoses from the first three pages (maximum five pages) of the search result, containing 30 documents, to see if the condition would fit the case record. As Google does not “suggest” a diagnosis, we selected the diagnosis that we felt would fit best with the case record. When none of the diagnoses found with Google fitted the case record well, we chose up to three most likely diagnoses. If one of the diagnoses was correct, we regarded the search as successful.
We suspect that using Google to search for a diagnosis is likely to be more effective for conditions with unique symptoms and signs that can easily be used as search terms, such as the one described by Greenwald.1
Searches are less likely to be successful in complex diseases with non-specific symptoms (case records 10 and 14) or common diseases with rare presentations (case record 18).
The efficiency of the search and the usefulness of the retrieved information also depend on the searchers' knowledge base. In this case, although we were blinded to the correct diagnosis, one author was a respiratory and sleep trainee and the other a rheumatologist; sometimes the diagnoses were evident to us, and this could have affected our choice of search terms. When choosing the “correct” diagnoses from a list of possible choices returned by Google, we tried to avoid using specialist knowledge but chose diagnoses that were ranked most prominently and seemed to fit the case record. Therefore, for case record 9, where we made the correct diagnosis of “hot tub lung,” searching with Google did not give enough prominence to hot tub lung for it to be considered the correct answer.
Patients doing a Google search may find the search less efficient and be less likely to reach the correct diagnosis. We believe that Google searches by a “human expert” (a doctor) have a better yield, as Google is exceedingly good at finding documents with co-occurrence of the signs/symptoms used as search terms and human experts are efficient in selecting relevant documents. Furthermore, doctors in training would find the Google searches educational and useful in formulating a differential diagnoses.
The role of diagnostician remains one of the most challenging and fulfilling roles of a physician. Physicians have been estimated to carry two million facts in their heads to fulfil this role.7
With medical knowledge expanding rapidly, even this may not be enough. Search engines allow quick access to an ever increasing knowledge base.8
Google gives users ready access to more than three billion articles on the web9
and has far exceeded PubMed as the search engine of choice for retrieving medical articles.10
Google has been so popular that the word has entered the English lexicon as a verb.11
Google Scholar, currently in beta form (www.scholar.google.com), is likely to be even more useful as it searches only peer reviewed articles.
Doctors and patients are increasing proficient with the internet and frequently use Google to search for medical information. Twenty five million people in the United Kingdom were estimated to have web access in 2001, and searching for health information was one of the most common uses of the web.12
Computers connected to the internet are now ubiquitous in outpatient clinics and hospital wards. Useful information on even the rarest medical syndromes can now be found and digested within a matter of minutes. Our study suggests that in difficult diagnostic cases, it is often useful to “google for a diagnosis.” Web based search engines such as Google are becoming the latest tools in clinical medicine, and doctors in training need to become proficient in their use.
What is already known on this topic
Doctors and patients are increasingly using the internet to search for health related information
Google is the most popular search engine on the world wide web
What this study adds
Searching with Google may help doctors to formulate a differential diagnosis in difficult diagnostic cases