Table 1.

Characteristics of the ten studies included in the systematic review on the diagnostic and triage accuracy of symptom checkers.

First author (year)	Study design	Participants	Intervention	Symptom checker(s) used	Comparator	Outcome measures
Hageman (2015)21	Prospective cross-sectional study	86 hand clinic patients	Outpatients prospectively input data and symptoms into symptom checker to guess diagnosis	WebMD	Diagnosis from a hand surgeon	Diagnostic accuracy (top 3)
Semigran (2015)1	Vignette cross-sectional study	45 standardised vignettes: 15 emergency 15 non-emergency 15 self-care	Patient data and symptoms from various cases input into 23 symptom checkers	Ask MD, BetterMedicine. DocResponse, Doctor Diagnose, Drugs.com, EarlyDoc, Esagil, Family Doctor, FreeMD, HMS Family Health Guide, Healthline, Healthwise, Healthy Children, Isabel, iTriage, Mayo Clinic, MEDoctor, NHS Symptom Checkers, Steps2Care, Symcat, Symptify, Symptomate, WebMD	True diagnosis and appropriate triage advice	Diagnostic accuracy (primary diagnosis, top 3 and top 20 results) Triage accuracy (overall, emergency, non-emergency, self-care)
Powley (2016)15	Prospective cross-sectional study	34 inflammatory arthritis patients	Patients completed NHS and WebMD symptom checkers with their presenting symptoms	NHS Choices, WebMD	Diagnosis from secondary care	Diagnostic accuracy (primary diagnosis, top 5)
Berry (2019)22	Retrospective cross-sectional study	ED records of 168 HIV/hepatitis C patients	Retrospective input of patient data into symptom checkers	Mayo Clinic, WebMD, Symptomate, Symcat, Isabel	Emergency department physician determined diagnosis	Diagnostic accuracy (primary diagnosis, top 3 and top 10) Triage accuracy
Nazario Arancibia (2019)16	Prospective cross-sectional study	214 low-priority ED patients	Patients interviewed using questions from symptom checker to produce differentials	Mediktor	Emergency department diagnosis	Diagnostic accuracy (primary diagnosis, top 3, top 5, and top 10)
Shen (2019)17	Vignette cross-sectional study	42 vignettes of ophthalmic conditions	Cases inputted into symptom checker to record results	WebMD	True diagnosis and appropriate triage advice	Diagnostic accuracy (primary diagnosis and top 3). Triage accuracy (emergency, non-emergency)
Gilbert (2020)23	Vignette cross-sectional study	200 primary care vignettes	Vignettes used to input into symptom checkers and to assess general practitioners (GPs)	ADA, Babylon, Buoy, K health, Mediktor, Symptomate, WebMD, YourMD	True diagnosis and GPs	Diagnostic accuracy (primary diagnosis, top 3 and top 5) Triage accuracy
Hill (2020)18	Vignette cross-sectional study	48 vignettes with ‘Australia-specific conditions’	Vignettes summarised and entered in symptom checkers	36 symptom checkers, 17 diagnostic only, 9 triage only advice. 10 that provide both.	True diagnosis and appropriate triage advice	Diagnostic accuracy (primary diagnosis, top 3 and top 10) Triage accuracy (emergency, non-emergency, self-care)
Yu (2020)19	Retrospective cross-sectional study	100 ED patient records	Retrospectively using patient records to input information into symptom checkers	Drugs.com FamilyDoctor	Given ED triage level	Triage accuracy
Yoshida (2021)20	Vignette cross-sectional study	27 vignettes of orofacial pain conditions	Vignettes of varied orofacial conditions input into symptom checkers	Esagil, FreeMD, Healthline, Isabel, Mayo Clinic, MEDoctor, Symcat, Symptify, Symptomate, WebMD, ADA	True diagnosis by resident in orofacial pain and oral medicine	Diagnostic accuracy (primary diagnosis, top 4)