Diagnosis of Bronchitis
Acute Bronchitis in Adults
Acute bronchitis is diagnosed clinically based on history and physical examination alone, without routine laboratory or radiologic testing. 1, 2
Clinical Diagnostic Criteria
The diagnosis requires:
- Cough lasting 1-3 weeks (with or without sputum production) as the predominant symptom 1, 2
- Viral upper respiratory prodrome (rhinorrhea, sore throat) preceding the cough 2
- Absence of pneumonia on clinical grounds 1, 2
- Exclusion of asthma, COPD exacerbation, and common cold as alternative diagnoses 1, 2
Key Physical Examination Findings
Look for these specific features:
- Wheezing or crackles on auscultation without focal consolidation 2
- Normal vital signs (heart rate <100 bpm, respiratory rate <24 breaths/min, temperature <38°C) 2
- Absence of focal consolidation, egophony, or fremitus on chest examination 2
When these reassuring findings are present, chest radiography is unnecessary. 2
Critical Diagnostic Pitfall: Undiagnosed Asthma
In patients with recurrent episodes of "acute bronchitis" (≥2 episodes in 5 years), 65% actually have undiagnosed mild asthma. 1, 2 This is the most commonly missed diagnosis. 3 Consider spirometry and bronchodilator challenge testing in these patients. 2
When Testing IS Indicated
Obtain chest radiography only if:
- Clinical findings suggest pneumonia (focal consolidation, high fever, tachycardia, tachypnea) 2
- Symptoms persist beyond 3 weeks, requiring evaluation for alternative diagnoses 1, 3
Bronchiolitis in Children (<2 Years)
Bronchiolitis is diagnosed entirely on clinical grounds using history and physical examination—radiographic and laboratory studies should NOT be obtained routinely. 1
Clinical Diagnostic Features
The diagnosis requires:
- Age <2 years (most commonly <12 months) 1
- Viral upper respiratory prodrome (rhinorrhea) followed by lower respiratory symptoms 1
- Constellation of findings: tachypnea, wheezing, rales, increased respiratory effort (grunting, nasal flaring, retractions) 1
- Typical seasonal pattern (winter months) 1
Essential Risk Stratification
Always assess these risk factors for severe disease: 1
- Age <12 weeks 1
- History of prematurity 1
- Hemodynamically significant congenital heart disease 1
- Chronic lung disease (bronchopulmonary dysplasia) 1
- Immunodeficiency 1
Severity Assessment
Evaluate these specific parameters:
- Respiratory rate (count for full 60 seconds; tachypnea ≥70/min suggests severe disease) 1
- Oxygen saturation (SpO2 <90% indicates need for supplemental oxygen) 1
- Feeding ability and hydration status 1
- Work of breathing (retractions, nasal flaring, grunting) 1
Why Routine Testing Is Harmful
Do not obtain chest radiographs routinely—25% of hospitalized infants with bronchiolitis have atelectasis or infiltrates that are misinterpreted as bacterial pneumonia, leading to unnecessary antibiotic use. 4 Radiographic findings do not change management in uncomplicated bronchiolitis. 1, 5
RSV testing has acceptable sensitivity/specificity but does not affect clinical outcomes or management in typical cases. 5 Testing may be useful for cohorting hospitalized patients but is not needed for diagnosis. 5
Chronic Bronchitis
Chronic bronchitis is diagnosed when chronic cough and sputum production occur on most days for at least 3 months per year for at least 2 consecutive years, after excluding other respiratory or cardiac causes. 2
Diagnostic Criteria
- Chronic productive cough (≥3 months per year for ≥2 consecutive years) 2
- Exclusion of other causes (asthma, bronchiectasis, heart failure, lung cancer) 2
- Exposure history (cigarette smoking, occupational/environmental exposures) 2
Common Diagnostic Error
88.4% of patients with self-reported or physician-confirmed "chronic bronchitis" do not actually meet standard diagnostic criteria. 2 This represents massive overdiagnosis. Ensure strict adherence to the temporal criteria above.
Chronic Cough After Acute Bronchitis
If cough persists beyond 8 weeks following acute respiratory infection, this is chronic cough—NOT postinfectious cough—and requires systematic evaluation for upper airway cough syndrome, asthma, GERD, and nonasthmatic eosinophilic bronchitis. 3
The differential diagnosis at this point includes:
- Upper airway cough syndrome (look for throat clearing, postnasal drip sensation, rhinosinusitis) 3
- Asthma (40% develop transient bronchial hyperresponsiveness post-infection, though this typically resolves by 6 weeks) 3
- GERD (may be triggered by vigorous coughing from initial illness) 3
- Pertussis (if paroxysmal cough, post-tussive vomiting, or inspiratory whoop present) 3
Obtain chest radiograph and spirometry at this stage. 3