Differentials
Coronavirus disease 2019 (COVID-19)
SIGNS / SYMPTOMS
Important to consider the current COVID-19 epidemiologic situation and any recent outbreaks. May give history of COVID-19 exposure or unwell contacts.
Differentiating bacterial pneumonia from COVID-19 is not usually possible from signs and symptoms. However, patients with viral pneumonia (including COVID-19) are less likely to have rapid development of symptoms and a productive cough with purulent sputum. They are more likely to have myalgia or pleuritic pain.[92] The presence of anosmia or ageusia (loss of smell or taste) may be useful as a red flag for the presence of COVID‐19.[93]
INVESTIGATIONS
Real-time reverse transcription polymerase chain reaction (RT-PCR): positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. Rapid antigen tests may also be used.
Chest imaging alone is unreliable in differentiating COVID-19 from other causes of pneumonia due to the inconsistency with which COVID-19 results in imaging findings. No single feature on chest x-ray is considered diagnostic for COVID-19. Imaging may be used to support the diagnosis, especially in cases where suspicion is high but other diagnostic testing has come back negative for COVID-19. The most common findings are ground-glass opacities and/or consolidation, with distribution commonly being bilateral and peripheral with basal zone predominance. Pleural effusion, cavitations, and pneumothorax are rarely seen.[94]
Acute bronchitis
SIGNS / SYMPTOMS
No dyspnea, no lung crackles, mild presentation. Often related to a viral upper respiratory tract infection.
INVESTIGATIONS
No consolidation on chest x-ray, with frequency related to viral infection.
Congestive heart failure
SIGNS / SYMPTOMS
Peripheral edema, cardiomegaly, hypotension.
INVESTIGATIONS
Bilateral interstitial pattern or pleural effusions seen on chest x-ray.
COPD exacerbation
SIGNS / SYMPTOMS
Increased expectoration and cough, and worsening of dyspnea against a background of COPD. Patient is often a smoker.
INVESTIGATIONS
Chest x-ray shows hyperinflation.
Asthma exacerbation
SIGNS / SYMPTOMS
Symptoms and signs of bronchospasm, with worsening of underlying lung disease.
INVESTIGATIONS
No consolidation on chest x-ray.
Bronchiectasis exacerbation
SIGNS / SYMPTOMS
Increased expectoration and cough, and worsening of dyspnea, with worsening of underlying lung disease. Infections are typically recurrent.
INVESTIGATIONS
No consolidation on chest x-ray.
Tuberculosis
SIGNS / SYMPTOMS
Typically a long history, often with constitutional symptoms. Many patients will have lived in an endemic area.
INVESTIGATIONS
Cavitation on chest x-ray, enlarged lymph nodes, positive purified protein derivative (PPD) skin testing.
Lung cancer or lung metastases
SIGNS / SYMPTOMS
Constitutional symptoms are common.
INVESTIGATIONS
Consolidation on chest x-ray 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 chest x-ray. Microbiology of pleural fluid may reveal infecting organism.
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