Table 4.
Symptoms and diagnoses examined in included studies.
| Author, date | Were participants symptomatic, asymptomatic, or previously symptomatica? | Type of symptoms examined | Did the study follow up whether Web use was followed by a diagnosis? |
| Attfield et al [6] | Previously symptomatic | General (any symptoms) | Not assessed |
| Briet et al [19] | Unclear, participants were users asking questions about symptomsb | Hand illness-related symptoms | Not assessed |
| Cartright et al [20] | Unclear, participants were users issuing symptom-related queries to a search engineb | Generalc | Not assessed |
| Chin [21] | Asymptomatic, participants were presented with a symptom vignette | Symptom vignettes included: pain and stiffness in the body; burning, itching, and sometimes tingling sensation on their body; feeling feverish and chilly after an overseas trip; fatigue, sudden weight gain and difficulty dealing with cold; however, results were not analyzed separately for different symptoms | Not applicabled |
| Chin & Fu [22] | Asymptomatic; participants were presented with a symptom vignette | General (participants received 6 different vignettes with different symptoms, not assessed separately) | Not applicabled |
| Cooper et al [23] | Asymptomatic; participants were presented with a list of symptoms | Symptoms related to gynecologic cancers | Not applicabled |
| Cumming et al [24] | Most symptomatic (448/492), but some asymptomatic (44/492) | Menopausal symptoms | Not assessed |
| De Choudhury et al [25] | Unclear, participants were users issuing symptom-related Tweets and queries to a search engineb | General, logs were filtered for references to symptoms using a comprehensive list of symptoms from the Merck medical dictionary | Not assessed |
| Fiksdal et al [26] | Previously symptomatic | General (any symptoms) | Not assessed |
| Fox & Duggan [1] | Previously symptomatic | General (any symptoms) | Participants were asked whether their diagnosis was confirmed by a health professional; 45% said it was confirmed, 35% did not present, 19% said it was not confirmed/inconclusive |
| Hay et al [27] | Symptomatic; participants were newly diagnosed rheumatology patient | Rheumatoid symptoms | Yes, patients’ diagnoses were gathered after the appointment or at follow-up appointment |
| Keselman et al [28] | Asymptomatic; participants received a symptom vignette | Symptoms typical of stable angina | Not applicabled |
| Lauckner & Hsieh [29] | Asymptomatic; participants received a symptom vignette | Symptom vignettes involved one of four symptoms: headaches, chest pain, muscle twitches, or abdominal pain, but the different symptoms were not analyzed separately | Not applicabled |
| Luger [30] | Asymptomatic; participants received a symptom vignette | Symptom vignettes involved either mononucleosis or scarlet fever | Not applicabled |
| Medlock et al [31] | Previously symptomatic | General (any symptoms) | Not assessed |
| Morgan et al [32] | Unclear, participants were users issuing symptom-related Tweets and queries to a search engineb | Symptoms related to any type of genetic or rare disease | Not assessed |
| Mueller et al [33] | 87 participants were symptomatic, 10 were asymptomatic but searching on behalf of someone else | Symptoms related to lung cancer | Not assessed |
| Norr et al [34] | Asymptomatic; participants viewed a list of symptoms | General (“websites focused on symptoms of medical conditions”) | Not applicabled |
| North et al [35] | Unclear, participants were users searching the MayoClinic website or using a telephone triageb | General (any symptoms) | Not assessed |
| Perez et al [36] | Asymptomatic; participants received a symptom vignette | One of two clinical symptom scenarios: (1) fever, mild headache, dry cough, and myalgia, suggestive of influenza, and (2) fever, severe headache, and stiff neck, suggestive of meningitis | Not applicabled |
| Powell et al [37] | Unclear, participants were users of the NHS websiteb | General (any symptoms) | Not assessed |
| Powley et al [38] | Symptomatic; participants were patients attending a secondary care based rheumatology clinic | Either clinically apparent synovitis or a new onset of symptoms consistent with inflammatory arthritis but without clinically apparent synovial swelling | Yes, rheumatological diagnosis was recorded after consultation |
| Rice [39] | Previously symptomatic | General (any symptoms) | Not assessed |
| Teriaky et al [40] | Symptomatic; participants were patients awaiting gastroenterology appointments | Symptoms related to gastroenterology | Not assessed |
| Thomson et al [41] | Symptomatic; participants were colorectal cancer patients | Symptoms related to colorectal cancer | Yes; all participants were diagnosed with colorectal cancer |
| White & Horvitz [5] | Logs: Unclear, participants were users issuing symptom-related queries to a search engineb; survey: previously symptomatic | Logs related to 3 common symptoms (headache, muscle twitches, and chest pain) | Not assessed |
| White & Horvitz [42] | Previously symptomatic | General (any symptoms) | Not assessed |
| White & Horvitz [43] | Unclear, participants were users issuing symptom-related queries to a search engineb | Queries related to any of 6 common symptoms: headache, chest pain, muscle twitches, abdominal pain, nausea, and dizziness | Not assessed |
| White & Horvitz [44] | Unclear, participants were users issuing symptom-related queries to a search engineb | Queries related to one of 3 symptoms: chest pain, muscle twitches, and abdominal pain | Not assessed |
| White & Horvitz [45] | Unclear, participants were users issuing symptom-related queries to a search engine | Generalc | Not assessed |
| White & Horvitz [46] | Unclear, participants were users issuing symptom-related queries to a search engineb | Generalc | Not assessed |
| Ybarra & Suman [47] | Previously symptomatic | General (any symptoms) | Not assessed |
a Symptomatic: participants experienced the symptoms at the time of the study; asymptomatic: participants did not have symptoms and were surveyed regarding fictional symptoms; previously symptomatic: participants were surveyed about symptoms they experienced previously.
b Participants were users asking questions about symptoms (could be own symptoms or asking on behalf of someone else).
c Any queries related to a comprehensive list of symptoms from the Merck medical dictionary.
d Patients were not symptomatic.