In an audit that is believed to be the first of its kind, Harvard Medical School researchers have tested 23 online “symptom checkers” and found that, though the programs varied widely in accuracy of diagnoses and triage advice, as a whole they were astonishingly inaccurate. Hannah Semigran, research assistant in health care policy, and Ateev Mehrotra, associate professor of health care policy, are the study coauthors.