History and exam
Key diagnostic factors
Key risk factors include smoking and exposure to infection.
Patients with acute bronchitis generally have a cough lasting for <30 days; however, some studies have shown that cough lingers for >30 days in about a quarter of patients. Consequently, acute bronchitis can still be present in patients with coughs that have persisted for >1 month.
The cough may be productive with clear, white, or discoloured sputum.
Acute bronchitis should only be diagnosed in a patient in whom underlying respiratory problems such as asthma have been excluded as causes. The main difference between asthma and acute bronchitis is the chronicity of bronchospasm. In asthma, bronchospasm is recurrent and progressive.
Acute bronchitis may be diagnosed once other illnesses such as pneumonia, congestive heart failure (CHF), and postnasal drip are excluded as causes. Rales on examination suggest pneumonia or CHF.
Other diagnostic factors
Because acute bronchitis is related to viral illnesses and atypical bacterial infections, exposure is the greatest risk for the disease. This accounts for the seasonal increase in winter months and in patients exposed to close contacts who are ill with a respiratory infection.
While cigarette smoking is clearly linked to chronic bronchitis and worsening asthma, there is scant population-based evidence that cigarette smoking increases the risk of acute bronchitis. However, because of the underlying bronchial inflammation present in smokers, there is conjecture that smokers are more likely to have more severe episodes and seek care when they develop acute bronchitis.
There is limited evidence for an association between household air pollution (from domestic solid fuel use) and the risk of acute lower respiratory infection.
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