Pneumonia Diagnostic Approach

Introduction to Diagnostic Testing

The British Thoracic Society recommends a testing approach for pneumonia that is stratified by severity and care setting, with outpatients with mild pneumonia requiring minimal to no testing, while hospitalized patients need chest radiography, basic laboratory work, and oxygenation assessment, with microbiological testing reserved for severe cases or specific clinical indications 1, 2, 3

The British Thoracic Society suggests that general investigations, including chest radiography, are not necessary for the majority of patients with suspected community-acquired pneumonia managed in the community 1, 3
The Infectious Diseases Society of America recommends that routine diagnostic tests to identify an etiologic diagnosis are optional for outpatients 2
Pulse oximetry should be considered in out-of-hours and emergency assessment centers for simple oxygenation assessment 1, 3

The British Thoracic Society recommends that all hospitalized patients should have chest radiograph, full blood count, urea, electrolytes, and liver function tests, and oxygenation assessment performed on admission 1, 3, 4
The European Respiratory Society suggests that arterial blood gas or pulse oximetry determinations, and basic blood chemistry including creatinine, urea nitrogen, aminotransferases, sodium, and potassium should be performed in hospitalized patients 6

The British Thoracic Society recommends that blood cultures are recommended for all hospitalized patients, preferably before antibiotic treatment is commenced 1, 3, 4, 7
The Infectious Diseases Society of America suggests that sputum collection is indicated when patients have severe CAP or have not responded to empirical antibiotic therapy 2
The European Respiratory Society recommends that Gram stain is recommended when a purulent sputum sample can be obtained and is processed timely 8

The Infectious Diseases Society of America recommends that for patients with severe CAP, blood cultures, urinary antigen test for Legionella pneumophila, and urinary antigen test for Streptococcus pneumoniae should be performed 2, 5
The British Thoracic Society suggests that paired serological tests for atypical pathogens, and pneumococcal antigen tests should be considered in severe CAP 1, 3, 4, 7

The Infectious Diseases Society of America recommends that testing should be performed when results are likely to change individual antibiotic management or have highest yield, including severe CAP requiring ICU admission, failure to respond to empirical therapy, and cavitary infiltrates 2
The British Thoracic Society suggests that serological tests should be extended to all hospitalized patients during outbreaks, and investigations for Legionella infection are recommended for all patients during outbreaks 1, 3, 4, 7

The European Respiratory Society recommends that natriuretic peptides, troponin, and ECG should be considered in patients with dyspnea to differentiate heart failure from pneumonia 5
The European Respiratory Society suggests that D-dimer, procalcitonin, and diagnostic thoracentesis should be considered in selected cases 5, 8

The European Respiratory Society recommends that trans-thoracic needle aspiration, and bronchoscopic protected specimen brush and bronchoalveolar lavage can be considered in selected cases 8