With more than one-third of US adults regularly using the Internet to self-diagnose, there has been a proliferation of online symptom checkers offering streamlined medical advice.
While it is important for pharmacists to remind patients that online symptom checkers are by no means conclusive, it is helpful to know where patients are looking, and even more helpful to offer advice about which ones may be most useful.
To determine this, a recent study published in BMJ audited 23 online symptom checkers using 45 standardized patient vignettes reflecting conditions that ranged from common to less common and low risk to life threatening. 
All symptoms checkers examined were free, publicly available, in English, and did not focus on a single type of condition.
Symptom checkers that listed the correct diagnosis within the first 3 results they provided were ranked as follows:

1.     Symcat – 71% accurate in diagnosis decision and triage advice
Symcat is a disease calculator that uses nearly 500,000 patient records to estimate the probability of a disease. Beyond offering diagnoses, Symcat facilitates appointment scheduling and maps nearby urgent care centers. It is also available on mobile platforms.

2.     Isabel – 69% accurate

Isabel is the Web-based Diagnosis Checklist System tool of Isabel Healthcare, a computer-based diagnostic aid company.

3.     AskMD – 68% accurate

AskMD is the symptom checker app for Sharecare, a social network that allows patients to maintain an online health profile. It was co-founded by Dr. Oz and WebMD founder Jeff Arnold.

4.     DocResponse – 67% accurate

DocResponse is developed and maintained by a group of board-certified physicians. It bills itself as a user-friendlier Web diagnostic tool than its competitors.

5.     iTriage – 64% accurate

iTriage is both a symptom checker and health literacy tool that allows patients to connect with care options and securely manage their health information. It is also available as a mobile app.

6.     Mayo Clinic – 59% accurate

This online diagnostic tool is maintained by the Mayo Clinic.

7.     FamilyDoctor – 56% accurate

FamilyDoctor is a health tool of the American Academy of Family Physicians. It provides symptom flowcharts that allow patients to easily arrive at a potential diagnosis.

 8.     Healthline – 53% accurate

Healthline is managed by experienced health care professionals in conjunction highly skilled writers in an effort to provide potential diagnosis information in plain language.

9.     HMS Family Health Guide – 52% accurate

The HMS Family Health Guide symptom checker is hosted by Harvard Medical School.

10. WebMD – 51% accurate

WebMD allows patients to check their symptoms, get related health information, and print a report out for their physician. It is also available as a mobile app.