Diagnosing Bronchitis
Acute Bronchitis is a Clinical Diagnosis
Acute bronchitis is diagnosed clinically based on acute cough with or without sputum production, and routine diagnostic testing should not be performed. 1, 2
Key Diagnostic Steps
1. Rule Out Pneumonia First
The most critical step is distinguishing acute bronchitis from pneumonia, which requires specific treatment and carries significant morbidity and mortality. 1
You can safely avoid ordering a chest radiograph if ALL four of the following are absent: 1
- Heart rate >100 beats/min
- Respiratory rate >24 breaths/min
- Oral temperature >38°C (100.4°F)
- Chest examination findings of focal consolidation, egophony, or fremitus
If any of these findings are present, obtain a chest radiograph to evaluate for pneumonia. 1 This approach is particularly important in elderly patients, who may present with fewer respiratory symptoms despite having pneumonia. 1
2. Consider Alternative Diagnoses
Acute bronchitis is often misdiagnosed when the actual cause is: 1, 2, 3
- Acute asthma exacerbation
- Acute exacerbation of chronic obstructive pulmonary disease (COPD)
- Common cold
- Pertussis (especially if cough persists >2 weeks with paroxysms, whooping sound, or post-tussive vomiting) 1, 3
- COVID-19 or influenza 2
3. Do NOT Order Routine Testing
For typical acute bronchitis, do not obtain: 1
- Viral cultures
- Serologic assays
- Sputum analyses
- Chest radiographs (if pneumonia criteria above are absent)
The responsible organism is rarely identified in clinical practice, and testing does not change management. 1 Note that purulent sputum does NOT distinguish between pneumonia and acute bronchitis. 1, 4
Epidemiologic Clues
Consider specific pathogens based on exposure history: 1
- Pertussis: Contact with confirmed case, severe paroxysmal cough, whooping sound, or post-tussive vomiting
- Mycoplasma or Chlamydia pneumoniae: Outbreaks in military personnel or college students
Chronic Bronchitis Diagnosis
Chronic bronchitis is diagnosed when a patient has chronic cough and sputum production occurring most days for at least 3 months per year for 2 consecutive years, after excluding other respiratory or cardiac causes. 1, 5
Essential History Elements
Obtain a complete exposure history including: 1
- Cigarette, cigar, and pipe smoking (responsible for 85-90% of cases) 5
- Passive smoke exposure
- Occupational and home environmental hazards
Recognizing Acute Exacerbations
Patients with stable chronic bronchitis who develop sudden worsening should be considered to have an acute exacerbation if they have: 1, 6
- Increased cough
- Increased sputum production
- Increased sputum purulence
- Increased shortness of breath
- Often preceded by upper respiratory infection symptoms
Reserve antibiotics for exacerbations only in patients with at least one cardinal symptom AND one risk factor: 6
Cardinal symptoms (need ≥1):
- Increased dyspnea
- Increased sputum production
- Increased sputum purulence
Risk factors (need ≥1):
- Age ≥65 years
- FEV1 <50% predicted
- ≥4 exacerbations in 12 months
- One or more comorbidities
Bronchiolitis in Children (Different Entity)
If your patient is a child under 2 years old, you are likely dealing with bronchiolitis, not bronchitis—these are distinct conditions. 1, 7, 8
Clinical Diagnosis in Children
Bronchiolitis is diagnosed by identifying: 7, 8
- Age <2 years
- Viral upper respiratory prodrome (rhinorrhea)
- Lower respiratory signs: tachypnea, wheezing, rales, cough
- Increased respiratory effort: grunting, nasal flaring, intercostal/subcostal retractions
Risk Factors for Severe Disease
- Age <12 weeks
- Prematurity
- Hemodynamically significant congenital heart disease
- Chronic lung disease (bronchopulmonary dysplasia)
- Immunodeficiency
- In utero smoke exposure
Do NOT Order Routine Tests in Children
The American Academy of Pediatrics recommends against routinely obtaining: 7
- Chest radiographs
- Laboratory studies
- RSV testing
These tests do not alter management, increase costs, and may lead to inappropriate antibiotic prescribing. 7
Key Physical Examination Points
- Count respiratory rate for full 60 seconds 7
- Tachypnea ≥70 breaths/minute suggests increased risk of severe disease 7
- Serial observations over time are necessary as the disease state varies 1, 7
- Assess effects on feeding, hydration, and mental status 7
Common Pitfalls to Avoid
Do not rely on sputum color or purulence to diagnose bacterial infection in acute bronchitis—this does not reliably differentiate viral from bacterial causes. 1, 4
Do not confuse acute bronchitis with chronic bronchitis exacerbations—the latter requires documented history of chronic productive cough and different management. 1, 5
Do not order chest radiographs reflexively—use the four clinical criteria to determine when imaging is truly needed. 1