Community-acquired pneumonia in adults (non COVID-19)
Differentials
Coronavirus disease 2019 (COVID-19)
SIGNS / SYMPTOMS
Residence in/travel history to an area with ongoing transmission, or close contact with a suspected/confirmed case of COVID-19 in the 14 days prior to symptom onset.
Differentiating community-acquired bacterial pneumonia from COVID-19 is not usually possible from signs and symptoms. However, patients with bacterial pneumonia are more likely to have rapid development of symptoms and purulent sputum. They are less likely to have myalgia, anosmia, or pleuritic pain.[109]
This topic covers pneumonia caused by COVID-19 as a differential diagnosis only. For more detail on the diagnosis and management of community-acquired pneumonia caused by COVID-19, see our topic Coronavirus disease 2019 (COVID-19)
INVESTIGATIONS
Real-time reverse transcription polymerase chain reaction (RT-PCR): positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA.
It is not possible to differentiate COVID-19 from other causes of pneumonia on chest imaging.
Acute bronchitis
SIGNS / SYMPTOMS
No dyspnoea, no lung crackles, mild presentation. Often related to a viral upper respiratory tract infection.
INVESTIGATIONS
No consolidation on CXR, with frequency related to viral infection.
Congestive heart failure
SIGNS / SYMPTOMS
Peripheral oedema, cardiomegaly, hypotension.
INVESTIGATIONS
Bilateral interstitial pattern or pleural effusions seen on CXR.
COPD exacerbation
SIGNS / SYMPTOMS
Increased expectoration and cough, and worsening of dyspnoea against a background of COPD. Patient is often a smoker.
INVESTIGATIONS
CXR shows hyperinflation.
Asthma exacerbation
SIGNS / SYMPTOMS
Symptoms and signs of bronchospasm, with worsening of underlying lung disease.
INVESTIGATIONS
No consolidation on CXR.
Bronchiectasis exacerbation
SIGNS / SYMPTOMS
Increased expectoration and cough, and worsening of dyspnoea, with worsening of underlying lung disease. Infections are typically recurrent.
INVESTIGATIONS
No consolidation on CXR.
Tuberculosis
SIGNS / SYMPTOMS
Typically a long history, often with constitutional symptoms. Many patients will have lived in an endemic area.
INVESTIGATIONS
Cavitation on CXR, enlarged lymph nodes, positive purified protein derivative (PPD) skin testing.
Lung cancer or lung metastases
SIGNS / SYMPTOMS
Constitutional symptoms are common.
INVESTIGATIONS
Consolidation on CXR may be multiple, with pleural effusion commonly seen.
Empyema
SIGNS / SYMPTOMS
Constitutional symptoms are common, usually associated with a recent respiratory infection.
INVESTIGATIONS
Pleural effusion seen on CXR. Microbiology of pleural fluid may reveal infecting organism.
Pulmonary embolism
SIGNS / SYMPTOMS
Suspect pulmonary embolism in a patient with acute onset of dyspnoea, pleuritic chest pain, or features of deep vein thrombosis. In general, symptoms developing within minutes are more suggestive of pulmonary embolism than of community-acquired pneumonia.
Cough is usually non-productive.
Fever is generally lower in pulmonary embolism (i.e., below 39°C [102.2°F]).[73]
INVESTIGATIONS
Multiple-detector computed tomographic pulmonary angiography (CTPA): direct visualisation of thrombus in a pulmonary artery; appears as a partial or complete intraluminal filling defect.
Pneumothorax
SIGNS / SYMPTOMS
May be difficult to differentiate on the basis of signs and symptoms. In general, symptoms developing within minutes are more suggestive of pneumothorax than of community-acquired pneumonia.
Spontaneous pneumothorax may occur as a complication of pneumonia.
INVESTIGATIONS
CXR: presence of a visceral pleural line.[114]
Hypersensitivity pneumonitis
SIGNS / SYMPTOMS
May be difficult to differentiate on the basis of signs and symptoms.
Acute hypersensitivity pneumonitis lasts only a few days and recurs with each additional exposure.
INVESTIGATIONS
Immunological response to causative antigen: positive.
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