Differentials

SIGNS / SYMPTOMS
INVESTIGATIONS
SIGNS / SYMPTOMS

Residence in/travel to a country/area or territory with local transmission, or close contact with a confirmed or probable case of COVID-19, in the 14 days prior to symptom onset. 

Signs and symptoms of viral pneumonia caused by COVID-19 and pneumonia caused by bacteria (either primary or secondary to COVID-19) are similar so it may be difficult to differentiate between the conditions clinically.[101]

COVID-19 viral pneumonia may be more likely if the patient presents with a history of typical COVID-19 symptoms for about a week, severe myalgia, anosmia, breathlessness, and absence of pleuritic pain.[101]

A bacterial cause of pneumonia may be more likely if the patient becomes rapidly unwell after only a few days of symptoms and presents with pleuritic pain, purulent sputum, and no history of typical COVID‑19 symptoms.[101]

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. 

SIGNS / SYMPTOMS
INVESTIGATIONS
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.

SIGNS / SYMPTOMS
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SIGNS / SYMPTOMS

Peripheral oedema, cardiomegaly, hypotension.

INVESTIGATIONS

Bilateral interstitial pattern or pleural effusions seen on CXR.

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.

SIGNS / SYMPTOMS
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SIGNS / SYMPTOMS

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

INVESTIGATIONS

No consolidation on CXR.

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.

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.

SIGNS / SYMPTOMS
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SIGNS / SYMPTOMS

Constitutional symptoms are common.

INVESTIGATIONS

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

SIGNS / SYMPTOMS
INVESTIGATIONS
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.

SIGNS / SYMPTOMS
INVESTIGATIONS
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.

SIGNS / SYMPTOMS
INVESTIGATIONS
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.[102]

SIGNS / SYMPTOMS
INVESTIGATIONS
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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