How accurate are online symptom checkers?

Members of the public are increasingly using the internet to research their health concerns. For example, the United Kingdom’s online patient portal for national health information, NHS Choices, reports over 15 million visits per month, and more than a third of adults in the United States regularly use the internet to self diagnose their ailments, using it both for non-urgent symptoms and for urgent symptoms such as chest pain. Using computerized algorithms, symptom checkers ask users a series