Table 1.

Characteristics of included studies (31 studies)

Main outcome area	Author year Country Reference	Study design	Sample/data size	Urgent or emergency care	Staff type conducting triage	Participants and service name	Comparator	Quality
User experience	Björkman 2018 Sweden44	Qualitative: 'Netnographic' method using information from online forums using six step	Data collected from 3 online forums	Urgent	Nurse	General population	None	High
User experience	O'Cathain 2014 England40	Quantitative: Survey	Survey sent to 1200 patients from 4 pilot sites, 1769 responded and were included for analysis	Urgent	Non-clinical call handler	General population	None	Medium
User experience	McAteer 2016 Scotland6	Mixed methods: survey and interviews	Survey: Age and sex-stratified random sample of 256 adults from each of 14 Scottish GP surgeries, final sample was 1190. Interviews: 30 semistructured interviews	Urgent	Non-clinical call handler	General population (National Health Service (NHS) 24 users and non-users)	Interviewees (from survey respondents) grouped into satisfied users, dissatisfied users and non-users	High
User experience	Rahmqvist 2011 Sweden41	Quantitative: Survey	Random sample of 660 callers, made at one call centre site in October 2008	Urgent	Nurse	General population	(1) Cases: those who disagreed with nurse advice and felt they needed higher level of care; (2) Controls: those who disagreed with nurse advice OR felt they needed higher level of care; (3) other callers	Medium
User experience	Goode 2004 England43	Qualitative: Interview study	60 interviews	Urgent	Nurse	General population	None	High
User experience	Winneby 2014 Sweden45	Qualitative: Interview study	8 semistructured interviews	Urgent	Nurse	General population	None	High
User experience	Goode 2004 England42	Qualitative: Interview study	10 semistructured interviews	Urgent	Nurse	Interviews focused on men	None	High
Patterns of triage advice	Payne 2001 England23	Routine data analysis	56 450 calls	Urgent	Nurse	General population	None—comparisons within digital triage call data	High
Patterns of triage advice	Elliot 2015 Scotland5	Routine data analysis	1 285 038 calls	Urgent	Nurse	General population	None—comparisons within digital triage call data	High
Patterns of triage advice	Zwaanswijk 2015 Netherlands25	Routine data analysis	895 253 patients	Urgent	Nurse (GP cooperative)	General population	Some comparison with non-digital triage	High
Patterns of triage advice	Njeru 2017 USA7	Routine data analysis	587 cases 587 controls	Urgent	Nurse	Those aged over 18— (callers with and without limited English proficiency)	Patients with limited English proficiency compared with English proficient	High
Patterns of triage advice	Jacome 2018 Portugal24	Routine data analysis	148 099 calls	Urgent	Nurse	General population (Older age groups 65+)	None - Comparisons within digital triage call data	High
Patterns of triage advice	Hsu 2011 England21	Routine data analysis	402 959 calls	Urgent	Nurse	Older age groups (aged over 65 years)	None	High
Patterns of triage advice	Cook 2013 England20	Routine data analysis	358 503 calls	Urgent	Nurse	children aged 0–15 (<1, 1–3 and 4–15 years))	Comparisons between age groups	Medium
Patterns of triage advice	North 2010 USA22	Routine data analysis	20 230 calls	Urgent	Nurse	General population (those with subscription and insurance)	Three comparison groups: (1)Triaged callers; (2) Emergency Department (ED) attendances; (3) Office (GP) visits. (Comparison of hospitalisation in these groups)	Medium
Patterns of triage advice	North 2011 USA19	Routine data analysis	Over the 3-year period: 105 866 adult calls (65% of the total calls). Of these, 14 646 (14%) were made by a surrogate on behalf of the patient.	Urgent	Nurse	General population (aged over 18)	Surrogate vs self calls	Medium
Service use following triage	Lattimer 2000 England32	Quantitative descriptive: Cost-effectiveness report from controlled trial	>14 000 Control group (n=7308 calls) Intervention group that is, Nurse telephone consultation (n=7184 calls)	Urgent	Nurse (within general practice cooperative)	General population	Usual care (referral to a General Practice) compared with nurse-led digital triage	Medium
Service use following triage	Munro 2000 England29	Routine data analysis	Study corresponds to the 1st year of operation, where 68 500 NHS direct calls from the 1.3 million people served.	Urgent	Nurse	All contacts with these immediate care services (at time spanning before and after introduction of call centre based service)	Service use in regions where digital triage service was introduced, compared with regions with no implementation	High
Service use following triage	Dale 2003 England36	Controlled trial	635 triaged calls 611 non-triaged calls	Emergency	Nurse and paramedic (within emergency control room)	General population, calling the emergency service for non-emergency concerns (only those aged 2+)	The control group not offered triage was compared with calls digitally triaged either by nurses or paramedics.	High
Service use following triage	Foster 2003 England27	Routine data analysis and data linkage	4493 calls, of which 193 were advised to go to Emergency Department (ED)	Urgent	Nurse	General population	Three comparison groups: Callers triaged to Emergency Department (ED), who attended Callers triaged to ED who did not attend Callers with different triage outcome who attended ED.	Medium
Service use following triage	Mark 2003 England46	Mixed methods (routine data analysis +interviews)	Numbers of calls analysed across 3 years: 5126 (year 1998) 5702 (1999) 4698 (2000)	Urgent	Nurse	General population	n/a	Low
Service use following triage	Sprivulis 2004 Australia34	Routine data analysis & data linkage	13 019 presentations to Emergency Department (ED) of which 842 were identified as having contacted Health-Direct within the 24 hours period prior to presentation.	Urgent	Nurse	General population—all patients who contacted the digital triage service during the 1-year study period	Patients who were digitally triaged prior to attending ED Patients who were not digitally triaged	High
Service use following triage	Dunt 2005 Australia30	Quantitative: four trials including surveys (self-reported service use)	Random sampling (350 households per trial site)	Urgent	Nurse	General population	2 sites using ‘standalone’ telephone triage which used ‘call centre software’ 2 embedded telephone triage sites using paper based protocols	Medium
Service use following triage	Munro 2005 England28	Quantitative: Surveys (care providers)	571 surveys sent (188/297) responses from GP cooperatives, (35/35) for ambulance services and (200/239) for emergency departments	Urgent	Nurse	Surveys sent to care providers (general use of services following NHS direct implementations)	n/a	Medium
Service use following triage	Stewart 2006 England37	Routine data analysis & data linkage	3312 calls to call centre based service, and 14 029 patients who attended Emergency Department (ED)	Urgent	Nurse	Children and young adults aged under 16	Patients advised through digital triage to attend ED Patients given alternative referral advice, through digital triage, but who still attended ED Patients referred to ED by their GP Self-referrals to ED	High
Service use following triage	Byrne 2007 England26	Quantitative: Survey	268 callers	Urgent	Nurse	General public with 3 symptom types (abdominal pain or cough and/or sore throat)	None	High
Service use following triage	Morimura 2010 Japan35	Routine data analysis	26 138 telephone consultations	Emergency	Nurse and call handler	General population	None	Medium
Service use following triage	Huibers 2013 Netherlands33	Quantitative: Questionnaires	7039 questionnaires returned (from a total of 13 953 sent)	Urgent	Nurse	General population (users who had a telephone contact with a nurse)	None	High
Service use following triage	Turner 2013 England38	Routine data analysis	400 000 calls to call centre based service in first year of operation analysed	Urgent	Nurse	General population	Matched sites: (1) Intervention sites: four digital pilot sites; (2)Control sites (North of Tyne, Leicester, Norfolk)	High
Service use following triage	Turbitt 2015 Australia31	Quantitative: Surveys	1150 parents attending Emergency Department (ED) (decline rate 19.9%)	Urgent	Nurse	Specific group	Some comparisons between parents who called and did not call but prior to attending ED	Medium
Service use following triage	Siddiqui 2019 Australia39	Routine data analysis and data linkage	12 741 triaged cases linked to 72.577 ED presentations	Urgent	Nurse	General population	None	High

ED, emergency department; GP, general practice.