From the Guidelines
A chest radiograph is the primary diagnostic test used to identify pneumonia, as it can demonstrate a demonstrable infiltrate, with or without supporting microbiological data, and is required for the routine evaluation of patients who are likely to have pneumonia. According to the Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults 1, the diagnosis of pneumonia is based on the presence of select clinical features and is supported by imaging of the lung, usually by chest radiography. Some key points to consider when diagnosing pneumonia include:
- Clinical features such as cough, fever, sputum production, and pleuritic chest pain
- Physical examination to detect rales or bronchial breath sounds, although this is less sensitive and specific than chest radiographs 1
- Pulse oximetry to screen for hypoxemia, which may suggest the presence of pneumonia or unsuspected hypoxemia in patients with diagnosed pneumonia 1
- Microbiological studies may support the diagnosis of pneumonia, but routine tests are frequently falsely negative and are often nonspecific 1
- In some cases, CT scans may be more sensitive, but the clinical significance of these findings when findings of radiography are negative is unclear 1
From the Research
Diagnostic Tests for Pneumonia
- Chest radiography (X-ray) is commonly used to diagnose community-acquired pneumonia (CAP) 2, 3, 4, 5, 6
- Computed tomography (CT) is more sensitive and specific than chest radiography, but is not routinely recommended for initial assessment of CAP patients 2
- Blood culture, sputum culture, fluid sample, bronchoscopy, and pulse oximetry are also used to identify pneumonia 3
- Lung ultrasound (LUS) may have diagnostic utility in pneumonia, particularly in low- and middle-income countries (LMICs) 5
Characteristics of Diagnostic Tests
- Chest X-ray has a sensitivity of 51.9% and specificity of 71.3% for identifying pneumonia, with uncertain results being prevalent 4
- CT is considered the reference standard for diagnosing pneumonia, but its use is limited due to cost and availability 2, 6
- LUS has higher sensitivity for identification of consolidation than CXR, but its practical utility in diagnosis and management of pneumonia is still being evaluated 5
Clinical Utility of Diagnostic Tests
- Chest radiography is useful for ruling in pneumonia radiographically, but a negative result performs poorly at ruling out disease 4
- Follow-up imaging with chest radiographs or computed tomography post-illness resolution may be used to identify treatment-resistant inflammation or unidentified underlying malignancies 6
- The available evidence does not support the routine use of CXR or LUS as essential tools in the diagnosis and initial management of severe pneumonia 5