Table 2.
Characteristics of the study populations of studies included in the review (N=32).
| Author | Study population | Setting | Sample size |
| Attfield et al [6] | 2 groups of 8 NHS patients: 1 group from a Patient Advice and Liaison Service (PALS) patient panel (43-81 years, mean 64) and one group of MSc students for HCI (25-42 years, mean 31) | UK | 16 |
| Briet et al [19] | Users asking hand surgery-related questions from a free online health consultation website | USA (American website; no restriction regarding location of website users) | 131 questions |
| Cartright et al [20] | A set of filtered logs from a toolbar deployed by the Windows Live search engine, containing at least 1 symptom | USA (English-language logs, but no restriction regarding location of users) | 2,329,231 actions (=queries issued to a search engine) |
| Chin [21] | Younger and older adults from a university community | USA | 69; 41 younger adults (18-35), 28 older adults (60-83) |
| Chin & Fu [22] | Younger and older adults from community of a medium-sized city | USA | 46, 23 younger (18-28) and 23 older (60-77) adults |
| Cooper et al [23] | Women aged 40-60 years | USA | 132 |
| Cumming et al [24] | Visitors of a UK-based menopause website | UK (UK website; no restriction regarding location of website users) | 539 |
| De Choudhury et al [25] | Survey: US adults 18-70 years (census representative sampling); Twitter: 15-month sample of Twitter’s Firehose stream, English-language Tweets relating to health; log: data from a major Web search engine | USA (survey with US residents, only English-language log data but not restricted to a certain country) | 210 survey respondents; 125,166,549 tweets; 174,605,024 searches |
| Fiksdal et al [26] | Adult, English-speaking members of the Olmsted County, MN community (where Mayo Clinic is located) and Mayo Clinic patients, employees, and family visitors | USA | 19 |
| Fox & Duggan [1] | Adults living in the United States | USA | 3014 |
| Hay et al [27] | English-speaking US adults (≥17 years) | USA | 120 |
| Keselman et al [28] | Lay individuals (convenience sample) | USA | 20 |
| Lauckner & Hsieh [29] | Students from an undergraduate communication course at a large Midwestern university | USA | 274 |
| Luger [30] | Older US adults, ≥50 years, community resident, without cognitive impairment, who owned a computer | USA | 79 |
| Medlock et al [31] | Members of a local senior (Christian) organization | Netherlands | 118 |
| Morgan et al [32] | Random sample of English-language inquiries posted by lay people to the question and answer section of the GARD website and inquiries sent via email | USA (American website but no restrictions on locale of users) | 278 inquiries, 68 from 2006 and 210 from 2011 |
| Mueller et al [33] | Adults living in UK with undiagnosed symptoms potentially related to lung cancer | UK | 97 |
| Norr et al [34] | Undergraduate students from a large university in the Southern United States. | USA | 56 |
| North et al [35] | All symptom assessment callers to Ask Mayo Clinic (telephone triage) and all clicks to specific symptoms on the symptom-checker page of MayoClinic.com | USA | 70,370 calls; 2,059,299 clicks |
| Perez et al [36] | Young adults aged 21-35 with experience of online health information and reported barriers to accessing health services | USA | 78 |
| Powell et al [37] | Users of the NHS Direct website | UK | 792 for survey, 26 for interviews |
| Powley et al [38] | Newly presenting patients with either clinically apparent synovitis or a new onset of symptoms consistent with inflammatory arthritis but without clinically apparent synovial swelling attending a secondary care based rheumatology clinic | UK | 34 |
| Rice [39] | US adults: respondents from studies conducted within the Pew Internet and American Life project | USA | 13,978 respondents in 2000 who reported health seeking online, 500 of these were telephone interviewed in 2001 |
| Teriaky et al [40] | Patients awaiting appointments at a general gastroenterology clinic in London, ON, Canada | Canada | 87 |
| Thomson et al [41] | Newly diagnosed colorectal cancer patients (<6 months) | USA | 242 |
| White & Horvitz [5] | Log data related to symptom queries (no mention of restriction by locale) from all major Web search engines (eg, Google, Yahoo!, or Live Survey): randomly selected employees of the Microsoft Corporation who had performed at least 1 health-related online search; survey: Microsoft employees | USA (survey with US residents, no restriction mentioned regarding locale for logs) | Logs: 8732 users with symptom-related queries; survey: 515 participants |
| White & Horvitz [42] | 5000 Microsoft employees were invited via email, from these volunteers were chosen who indicated in a prescreening that they searched the Web for medical information | USA | 515 survey respondents |
| White & Horvitz [43] | Logs from windows live browser toolbar, English-speaking USA relating to 6 basic symptoms | USA (log data issued from US locale) | “Many thousands of logs were mined” |
| White & Horvitz [44] | Logs from consenting Windows live toolbar users over a 6-month period relating to 3 symptoms: chest pain, muscle twitches, abdominal pain | USA (log data issued from US locale) | 700 queries with symptom to HUI transition; 700 queries with symptoms to no HUI transition |
| White & Horvitz [45] | Logs from consenting Windows live toolbar users over a 3-month period | USA (log data issued from US locale) | 169,513 queries |
| White & Horvitz [46] | Log data related to symptoms queries generated in English-speaking US locale | USA (log data issued from US locale) | 2070 symptom queries from 714 users |
| Ybarra & Suman [47] | Americans living throughout the 50 states and the District of Columbia | USA | Year 1=2104; year 4: 2010, 570 of these were year 1 participants |