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Table 1 Characteristics of studies reporting the etiology of community acquired pneumonia (CAP)

From: Etiology of community-acquired pneumonia in adults: a systematic review

Nature of the microbiologic studies

Bacteria only

Bacteria & ‘atypicals’ a

Bacteria, ‘atypicals’ & viruses

Modern Studies: Bacteria and:

PCR for ‘atypicals’

PCR for viruses

PCR for ‘atypicals’ and viruses

Number of studies

25

37

46

16

10

12

Publication years

1945–2010

1984–2020

1967–2017

1999–2020

2008–2019

2005–2019

Study setting

 Inpatient only

8653

14,281

23,555

6790

6260

4399

 Inpatient/outpatient

118

3786

3512

1069

5295

2752

 Outpatient only

610

1368

226

0

0

0

Number of CAP patients

9381

19,435

27,293

7859

11,555

7151

Specifies antibiotic exposure prior to microbiologic testing

687 (7.3%)

3104 (16%)

4203 (15.4%)

1074 (13.7%)

2085 (18%)

966 (13.5%)

Number of patients with no etiology determined

6293 (67.1%)

11,663 (60.0%)

13,704 (50.2%)

4484 (57.1%)

5823 (50.4%)

4380 (61.3%)

  1. a “Atypicals” is a term used loosely in publications to refer to Mycoplasma, Chlamydophila, Legionella and/or Coxiella