Table 1.

Study characteristics

Study characteristics	Number of papers	References
Study design
Observational	12	[18–29]
Case–control	10	[30–39]
Cross-sectional	1	[40]
Participant age
Adults (≥ 18 years)	9	[18, 22, 24, 25, 27, 30, 32, 35, 40]
Children (< 18 years)	5	[20, 23, 29, 33, 38]
Mixed adults and children	9	[19, 21, 26, 28, 31, 34, 36, 37, 39]
Recruitment location
Primary care	14	[19, 20, 22, 23, 25, 26, 28, 31, 32, 34, 36–39]
Outpatient/inpatient	3	[24, 27, 35]
Emergency department	3	[18, 30, 33]
Community	3	[21, 29, 40]
Number of study participants
< 500	3	[28, 29, 38]
500–1000	2	[37, 39]
1001–2000	7	[20, 26, 27, 30, 31, 33, 40]
2001–5000	3	[32, 35, 36]
5001–10,000	1	[21]
> 10,000	7	[18, 19, 22–25, 34]
Primary RTI investigated
Community-acquired pneumonia	15	[18, 22, 25–28, 30–38]
Influenza-like-illness	2	[21, 24]
Lower RTI	2	[20, 23]
Any RTI	4	[19, 29, 39, 40]