TABLE 1

Characteristics of the studies

First author [ref.]	Study setting	Study design	Patient population	Patients n	Viral tests	Age years	Male %	Aims	Mortality %
Angeles Marcos [3]	Spain, 2003–2004, inpatient	Prospective cohort	Patients aged >14 years admitted to the hospital with CAP	198	PCR, IFA, culture, serology	70 (median)	58	Incidence and characteristics of viral CAP, and yield of tests for viral infection	2.5
van Gageldonk-Lafeber [5]	The Netherlands, 2007–2010, inpatient	Prospective cohort	Patients aged >18 years with CAP in the ED	339	PCR	66 (median)	62.5	Aetiology of CAP	Not reported
Hara [6]	Thailand, 2006–2008, inpatient	Prospective cohort	Patients aged >16 years admitted to the hospital with CAP	119	PCR	55 (mean)	71.4	Aetiology of CAP	18.5
Holm [22]	Denmark, 2002–2003, inpatient and outpatient	Prospective cohort	Patients aged >18 years with suspected CAP seen in outpatient clinic	48	PCR	50 (median)	49	Aetiology of CAP and outcomes	0
Mermond [7]	New Caledonia, 2006–2007, inpatient	Prospective cohort	Patients aged >16 years admitted to the hospital with CAP	137	PCR, IFA	58 (median)	58.4	Aetiology of CAP, performance of tests, and assessment of vaccination-preventable proportion of causative organisms	5.8
Jennings [8]	New Zealand, 1999–2000, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	304	PCR, IFA, culture, serology	70 (median)	52	Aetiology of CAP and characteristics of viral pneumonia	6.8 (only reported for viral subset)
Luchsinger [9]	Chile, 2005–2007, inpatient and outpatient	Prospective cohort	Patients aged >18 years presenting with CAP	356	PCR, IFA, culture, serology	61 (median)	53.6	Aetiology of CAP and relationship between severity and pathogen	7.8
Takahashi [10]	Vietnam, 2009–2010, inpatient	Prospective cohort	Patients aged >15 years admitted to the hospital with CAP	174	PCR	42 (median)	52	Incidence, aetiology and clinical features of CAP	9.8
Wiemken [11]	USA, 2008–2011, inpatient ICU	Prospective cohort	Patients aged >18 years with CAP admitted to the ICU	393	PCR	52 (mean)^#	56^#	Incidence of respiratory viruses in CAP patients in ICU	Not reported
Choi [2]	Republic of Korea, 2010–2011, inpatient	Retrospective analysis of a prospective cohort	Patients aged >18 years admitted to the hospital with severe CAP	64	PCR, culture	49 (mean)	76.6	Role of viral infection in patients with severe CAP	32.8
Templeton [1]	The Netherlands, 2000–2002, inpatient and outpatient	Prospective cohort	Patients aged >18 years with CAP	105	PCR, culture, IFA, complement fixation	>60 (50% of patients)	71	Aetiology of CAP	3.8
Musher [12]	USA, 2011–2012, inpatient	Prospective cohort	Patients admitted to a Veteran Affairs hospital	259	PCR	70 (mean)	95.7	Yield of traditional and new diagnostic tests	Not reported
Shibli [34]	Israel, 2006–2007, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	126	PCR, DNA/RNA genomic extraction, serology	58.3 (mean)	57.9	Identify common pathogens causing CAP in hospitalised patients and evaluate correlation of aetiology and disease severity	3.96
Sangil [33]	Spain, 2009–2010, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	131	Multiplex PCR, serology	64.4 (mean)	68.7	Determine aetiology of CAP by adding PCR to conventional methods and describe clinical and laboratory features between patients with bacterial and viral CAP	5.3
Johansson [26]	Sweden, 2004–2005, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	184	PCR, serology, viral culture	61.3 (mean)	51	Determine aetiology of CAP among adults using new PCR platform and conventional methods	3.8
Huijskens [24]	The Netherlands, 2008–2009, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	408	PCR, serology	68 (median)	61.3	Evaluate potential for targeted diagnostics and directed treatment	39
Saito [32]	Japan, 1999–2000, outpatient and inpatient	Prospective cohort	Patients aged >17 years admitted to the hospital with CAP	232	PCR, antigen immunoassay, serology	60 (mean)	57.8	Identify aetiology of CAP	1.7
Yin [36]	China, 2008–2009, infectious disease outpatient clinic	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	215	PCR	36.1 (mean of those reported)	47.1 (of those with aetiologies)	Evaluate Japanese Respiratory Society guidelines for identification of Mycoplasma pneumoniae	0
Diederen [20]	The Netherlands, 1998–2000, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	242	PCR, immunoassay/ELISA, serology	Not reported	Not reported	Detection of respiratory viruses and Legionella by PCR in CAP patients	9.5
Hohenthal [21]	Finland, 1999–2004, inpatient	Prospective cohort	Patients aged >16 years admitted to the hospital with CAP	384	PCR, immunoassay/IFA, serology	49.8 (mean)	52.3	Assess utility of rapid micro tests in different disease severities of CAP	Not reported
Lieberman [30]	Israel, Nov 2004–March 2005 and Nov 2005–April 2006, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	183	PCR	59.5 (mean)	57	Identify viruses in CAP versus control versus lower respiratory infections	Not reported
Kim [29]	Republic of Korea, 2010–2013, inpatient and outpatient	Retrospective cohort	Patients aged >18 years admitted to the hospital with CAP	327	PCR, immunoassay for influenza antigen	67 (mean) in viral pneumonia; 70 (mean) in nonviral pneumonia	72% in viral CAP; 78% in nonviral CAP	Investigate predictors of viral CAP	18.9
Karhu [28]	Finland, 2008–2013, inpatient ICU	Prospective cohort	Patients aged >18 years admitted to the hospital with severe CAP	49	PCR	54 (median)	42.9	Evaluate presence and course of viral infections in ventilated patients using PCR	12.2
Holter [23]	Norway, 2008–2011, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	264	PCR, serology	66 (mean)	52	Describe aetiology and evaluate diagnostic results	3.7
Qu [31]	China, 2010–2012, inpatient and outpatient	Prospective cohort	Patients aged >14 years admitted to the hospital with CAP	954	PCR	45.2 (mean)	56.6	Investigate respiratory virus aetiology in adolescents and adults with CAP, by age and PSI	0.4
Charles [17]	Australia, 2004–2006, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	865	PCR, serology for influenza	65.1 (mean)	60.7	Evaluate aetiology, severity assessment tools and outcomes of CAP	5.6
Viasus [35]	Spain, 2010–2011, inpatient	Prospective cohort	Adults admitted to the hospital with CAP	747	PCR	65 (median)	56.8	Evaluate aetiology, clinical features and prognosis of CAP	8.2
Das [19]	France, 2011–1012, ED	Prospective cohort	Patients aged >18 years presenting to the ED with CAP	125	PCR	65 (mean)^#	49^#	Evaluate aetiology of CAP	Not reported
Jain [25]	USA, 2010–2012, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	2259	PCR, serology	57 (median)	Not reported	Population-based surveillance study of CAP aetiology	2
Johnstone [27]	Canada, 2004–2006, inpatient	Prospective cohort	Patients aged >18 years admitted to the hospital with CAP	193	NAT, IFA	71 (median)	51	Describe the pathogens, clinical presentation and outcomes of patients with CAP	3
Cillóniz [18]	Spain, 2003–2010, inpatient ICU	Prospective cohort	Patients aged >18 years admitted to the ICU with CAP	362	PCR, IFA	63 (mean)	64	Study the prevalence, clinical characteristics and outcomes of severe CAP in the ICU	10

CAP: community-acquired pneumonia; IFA: immunofluorescence assay; ED: emergency department; ICU: intensive care unit; PSI: pneumonia severity index; NAT: nucleic acid amplification tests. ^#: for all patients, including some not included in our analysis.