Diagnosing Acute Bronchitis

Primary Diagnostic Criteria

The American College of Chest Physicians recommends that acute bronchitis be diagnosed in patients presenting with sudden onset of cough (with or without sputum) lasting less than 3 weeks, after excluding pneumonia, asthma exacerbation, chronic bronchitis exacerbation, and other serious conditions 1, 2
The diagnosis requires acute cough as the predominant symptom, with or without sputum production, and duration less than 3 weeks, which distinguishes it from chronic cough 1, 2
The absence of pneumonia and other serious respiratory conditions is also a crucial criterion for diagnosing acute bronchitis 1, 2

The American College of Chest Physicians states that the most important diagnostic task is excluding pneumonia, which requires different management and carries significant morbidity and mortality if untreated 1, 2
If all four of the following are absent, pneumonia is sufficiently unlikely that chest radiography can be omitted: heart rate > 100 beats/min, respiratory rate > 24 breaths/min, oral temperature > 38°C, and focal chest examination findings 3, 4, 1, 2

The American College of Chest Physicians recommends that for immunocompetent adults with suspected acute bronchitis, routine testing such as viral cultures, sputum cultures, respiratory tract samples for viral PCR, spirometry, and serum C-reactive protein or procalcitonin is not recommended 5, 1, 2

The American College of Chest Physicians suggests considering specific pathogens based on exposure history, such as pertussis, Mycoplasma, or Chlamydia pneumoniae 3, 4, 1, 2

Before confirming acute bronchitis, it is essential to rule out other conditions such as asthma, acute exacerbation of chronic bronchitis, common cold, and heart failure exacerbation 1, 2, 6, 7

The American College of Chest Physicians advises against assuming purulent sputum indicates bacterial infection, as sputum color reflects inflammatory cells from either viral or bacterial causes and should not guide antibiotic decisions 3, 7
Chest X-rays should not be ordered in healthy, non-elderly adults with normal vital signs and normal lung examination, as pneumonia is uncommon in this population 8

The diagnostic algorithm for acute bronchitis involves checking vital signs and performing a chest examination, and if all four pneumonia criteria are absent and the patient is < 60 years, diagnosing acute bronchitis clinically without a chest X-ray 3, 4, 8
If any pneumonia criteria are present or the patient is ≥ 60 years, a chest X-ray should be obtained to rule out pneumonia 3, 4, 8

The absence of egophony is one of the key criteria used to rule out pneumonia and confirm a diagnosis of bronchitis, according to the American College of Chest Physicians 9, 10, 11, 12, 13, 14
The American College of Chest Physicians and American College of Physicians specify that if all four of the following are absent, pneumonia is ruled out and bronchitis can be diagnosed clinically: heart rate >100 beats/min, respiratory rate >24 breaths/min, oral temperature >38°C is not a criterion due to missing reference, and chest examination findings of focal consolidation, egophony, or fremitus, with heart rate and respiratory rate being relevant 9, 10, 11, 13
The American College of Physicians emphasizes that focal chest examination findings, including egophony, distinguish pneumonia from bronchitis and change the diagnostic approach entirely 11

Egophony is a change in voice timbre caused by solid tissue, including consolidated lung from pneumonia, interposed between the resonating airways and the stethoscope, reflecting lung consolidation with fluid or inflammatory exudate filling the alveoli, which is the hallmark of pneumonia, not bronchitis 11
If egophony is detected during a chest examination, pneumonia rather than bronchitis should be suspected, and this finding warrants chest radiography to confirm or exclude pneumonia 9, 10, 11