Differentials
Viral upper respiratory infection (URI)
SIGNS / SYMPTOMS
Symptoms of adenovirus, human metapneumovirus, human parainfluenza virus, influenza, respiratory syncytial virus, and rhinovirus may be like those of pertussis.
INVESTIGATIONS
Antigen detection, culture, or nucleic acid amplification test (NAAT) of nasopharyngeal swab or aspirate. A negative test for pertussis is consistent with URI but does not exclude pertussis.
Community-acquired pneumonia (CAP)
SIGNS / SYMPTOMS
Infections caused by Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Chlamydia trachomatis may be associated with protracted and paroxysmal or 'staccato' cough.
Fever, history of productive cough, history of respiratory disease (e.g., asthma).
Signs of pneumonia on auscultation.
INVESTIGATIONS
Culture or NAAT of nasopharyngeal swab, nasopharyngeal aspirate, sputum, or bronchoalveolar lavage fluid. A negative test for pertussis is consistent with CAP but does not exclude pertussis.
CXR may show evidence of infiltrates. CXR is normal in uncomplicated pertussis.
Tuberculosis
SIGNS / SYMPTOMS
A chronic cough may be present in infections caused by Mycobacterium tuberculosis. The cough is generally not paroxysmal, and may be accompanied by fever, weight loss or failure to thrive, night sweats, and chills.
INVESTIGATIONS
A positive tuberculin skin test or interferon-gamma release assay typically develop within 10 weeks of infection, but do not distinguish between latent and active disease. Culture or nucleic acid amplification from sputum, gastric aspirate, bronchoalveolar wash fluid, pleural fluid, or other body fluids or tissues. Chest radiographs are typically abnormal in active disease, with mediastinal adenopathy, atelectasis, lobar or miliary infiltrates, pleural effusion, or cavitation.
Upper airway pathology
SIGNS / SYMPTOMS
Postnasal drip, chronic rhinitis, and sinusitis may be associated with cough syndromes, more commonly in adults than in children. Typically, these disorders present with prominent nasal discharge and the cough is not paroxysmal. Symptoms may be seasonal, and patients may have a personal or family history of other allergic disorders.
INVESTIGATIONS
The clinical and natural history usually distinguish between these conditions and pertussis. Response to appropriate therapy.
Chronic pulmonary disease
SIGNS / SYMPTOMS
A chronic cough may be present in individuals with chronic pulmonary disease, including asthma, chronic obstructive pulmonary disease, cystic fibrosis, bronchiectasis, interstitial lung disease, and lung cancer. Persistent cough may be a complication of drug therapy, especially ACE inhibitors. Symptoms are generally slowly progressive or intermittent and the cough is not paroxysmal. Sputum production may be prominent.
INVESTIGATIONS
The clinical and natural history usually distinguish between these conditions and pertussis. Chest radiographs or CT are typically abnormal. Pulmonary function tests may suggest obstructive or reactive airways disease.
Gastro-oesophageal reflux disease
SIGNS / SYMPTOMS
Gastro-oesophageal reflux is a relatively common cause of cough in adults. Patients may complain of sub-sternal chest pain, regurgitation, or hoarseness. The cough is not typically paroxysmal.
INVESTIGATIONS
Clinical and natural history. Oesophageal pH monitoring, upper oesophageal endoscopy, oesophageal manometry.
Aspiration
SIGNS / SYMPTOMS
Patients may have a history of impaired consciousness, swallowing dysfunction from neurological disease, or congenital or acquired disorders of the upper gastrointestinal tract. There may be coughing or choking with eating or recurrent pneumonia. Cough is highly variable, but not typically frequent or paroxysmal.
INVESTIGATIONS
Chest radiographs may demonstrate non-specific infiltrates and atelectasis. Swallowing evaluation, videofluoroscopic swallow study, or gastro-oesophageal scintigraphy, laryngoscopy, upper gastrointestinal endoscopy, and direct or indirect bronchoscopy.
Foreign body aspiration
SIGNS / SYMPTOMS
Most common in children aged <3 years but may occur at any age. Symptoms vary according to the site and severity of obstruction. The classic triad of cough, wheezing, and decreased breath sounds occurs in only about half of patients but is highly sensitive when present. There may be a history of choking, dyspnoea, stridor, cyanosis, and, if diagnosis is delayed, recurrent or persistent pneumonia.
INVESTIGATIONS
Rigid bronchoscopy with foreign body removal is both diagnostic and therapeutic. Chest radiography may demonstrate local hyperinflation, atelectasis, or a persistent pulmonary infiltrate. Chest CT is more sensitive. Fluorography may demonstrate air trapping or a mediastinal shift.
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