What are the diagnostic criteria for bronchitis?

Diagnostic Criteria for Bronchitis

The diagnosis of bronchitis is primarily clinical, based on history and physical examination findings, with acute bronchitis characterized by cough lasting 1-3 weeks accompanied by lower respiratory tract inflammation without evidence of pneumonia. 1

Acute Bronchitis Diagnostic Criteria

Key Clinical Features

• Acute cough lasting 1-3 weeks (the hallmark symptom) 2, 3
• Viral upper respiratory prodrome (rhinorrhea, sore throat) 1
• Cough with or without sputum production 1
• Absence of pneumonia, common cold, acute asthma, or exacerbation of chronic bronchitis 1

Physical Examination Findings

• Wheezing or crackles may be present on auscultation 1
• Increased work of breathing (less common in adults than children) 1
• Normal vital signs (absence of high fever, tachycardia, tachypnea) 1

Ruling Out Pneumonia

• The absence of the following findings reduces the likelihood of pneumonia sufficiently to eliminate the need for chest radiography: 1
  • Heart rate >100 beats/min
  • Respiratory rate >24 breaths/min
  • Oral body temperature >38°C
  • Chest examination findings of focal consolidation, egophony, or fremitus

Diagnostic Testing

• Routine laboratory and radiologic studies are not recommended for diagnosis of uncomplicated acute bronchitis 1
• No routine investigation with chest x-ray, spirometry, peak flow measurement, sputum for microbial culture, respiratory tract samples for viral PCR, serum C-Reactive Protein (CRP) or procalcitonin 1

When to Consider Additional Testing

• If symptoms persist or worsen, reassessment and targeted investigations should be considered 1
• Consider pertussis in patients with cough persisting >2 weeks accompanied by paroxysmal cough, whooping, or post-tussive emesis 3
• Consider asthma if there are recurrent episodes (65% of patients with recurrent bronchitis may have mild asthma) 1

Chronic Bronchitis Diagnostic Criteria

Chronic bronchitis is diagnosed when a patient has chronic cough and sputum production occurring on most days for at least 3 months and for at least 2 consecutive years when other respiratory or cardiac causes of chronic productive cough are ruled out. 1

Key Diagnostic Features

• Chronic cough and sputum expectoration occurring on most days for at least 3 months 1
• Symptoms present for at least 2 consecutive years 1
• Exclusion of other respiratory or cardiac causes of chronic productive cough 1

Risk Factors to Assess

• Cigarette, cigar, and pipe smoke exposure 1
• Passive smoke exposure 1
• Hazardous environmental exposures in home and workplace 1

Pitfalls in Diagnosis

• Overdiagnosis is common - 88.4% of patients with self-reported or physician-confirmed diagnoses of chronic bronchitis do not meet standard criteria 1
• The presence of colored (e.g., green) sputum does not reliably differentiate between bacterial and viral lower respiratory tract infections 2
• Recurrent episodes of "acute bronchitis" may represent undiagnosed asthma and warrant pulmonary function testing 1
• Differential diagnoses that must be ruled out include: 1, 3
  • Pneumonia
  • Asthma
  • Chronic bronchitis in smokers
  • Bronchiectasis
  • Acute rhinosinusitis
  • Pertussis

Special Considerations

• In patients with persistent or worsening symptoms, consider: 1
  • Chest x-ray
  • Sputum for microbial culture
  • Peak expiratory flow rate recording(s)
  • Complete blood count and inflammatory markers such as CRP
• Patients with underlying conditions (COPD, immunocompromise) may require more extensive evaluation 1
• Antibiotic therapy should be considered only if a complicating bacterial infection is suspected or if the patient is at increased risk of developing pneumonia (e.g., patients ≥65 years) 1, 3

Remember that acute bronchitis is predominantly viral in etiology (89-95% of cases) and typically resolves within three weeks, which should be emphasized to patients to manage expectations and reduce unnecessary antibiotic use 4, 3.