Differentials

Coronavirus disease 2019 (COVID-19)

SIGNS / SYMPTOMS
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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
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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
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SIGNS / SYMPTOMS

Peripheral oedema, cardiomegaly, hypotension.

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Bilateral interstitial pattern or pleural effusions seen on CXR.

COPD exacerbation

SIGNS / SYMPTOMS
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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
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SIGNS / SYMPTOMS

Symptoms and signs of bronchospasm, with worsening of underlying lung disease.

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No consolidation on CXR.

Bronchiectasis exacerbation

SIGNS / SYMPTOMS
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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
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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
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SIGNS / SYMPTOMS

Constitutional symptoms are common.

INVESTIGATIONS

Consolidation on CXR may be multiple, with pleural effusion commonly seen.

Empyema

SIGNS / SYMPTOMS
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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
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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]).[74]

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
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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
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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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