How to differentiate and manage a patient with symptoms of acute bronchitis versus upper respiratory tract infection (URTI), particularly in high-risk populations such as the elderly or those with chronic respiratory diseases?

Differentiating Acute Bronchitis from URTI

Acute bronchitis and URTI exist on a clinical continuum and are often indistinguishable in practice—both are predominantly viral, self-limited conditions that do not require antibiotics, with the critical distinction being the exclusion of pneumonia rather than differentiating between upper and lower tract involvement. 1, 2

Clinical Overlap and Diagnostic Reality

• Approximately 70% of adults presenting with acute cough have an upper respiratory tract infection, making URTI the most common diagnosis in patients with cough illness. 3, 1
• Clinicians are inconsistent in distinguishing acute bronchitis from other acute respiratory tract infections—some require productive cough, others insist on purulent sputum, but these distinctions lack clinical validity. 3
• The predominance of cough with accompanying features suggestive of upper respiratory infection (sore throat, rhinorrhea) is typically used to distinguish bronchitis from other URTIs, though this differentiation has limited therapeutic implications since both are viral. 3

The Critical Differentiation: Ruling Out Pneumonia

The primary evaluation goal is excluding pneumonia, not differentiating bronchitis from URTI. 3, 2

Clinical Prediction for Pneumonia

Suspect pneumonia when ANY of the following are present: 3, 2

• New focal chest signs on examination (rales, egophony, fremitus)
• Dyspnea or tachypnea (respiratory rate >24 breaths/min)
• Pulse rate >100 beats/min
• Fever lasting >4 days or temperature >38°C

Pneumonia is sufficiently unlikely to omit chest radiography when ALL four of the following are absent: 3, 2

• Heart rate >100 beats/min
• Respiratory rate >24 breaths/min
• Oral temperature >38°C
• Focal chest examination findings

Role of C-Reactive Protein

When pneumonia is suspected, CRP testing provides valuable diagnostic information: 3, 2

• CRP <20 mg/L with symptoms >24 hours makes pneumonia highly unlikely
• CRP >100 mg/L makes pneumonia likely
• If doubt persists after CRP testing, obtain chest X-ray 3

Special Considerations in High-Risk Populations

Elderly Patients (≥65 years)

Maintain a high index of suspicion for pneumonia in elderly patients, as they present with fewer typical respiratory symptoms and atypical disease presentations. 3, 4

Consider chest X-ray even with fewer clinical findings when the following risk factors are present: 3, 2

• Age ≥65 years
• Presence of COPD, diabetes, or heart failure
• Previous hospitalization in the past year
• Current oral glucocorticoid use
• Antibiotic use in the previous month
• General malaise or confusion/diminished consciousness

Patients with Chronic Respiratory Disease

Consider underlying COPD or asthma when patients present with persistent cough and at least TWO of the following: 3, 2

• Wheezing (as sign or symptom)
• Previous consultations for wheezing or cough
• Prolonged expiration
• Smoking history
• Symptoms of allergy

Up to 45% of patients with acute cough lasting >2 weeks have undiagnosed asthma or COPD, making lung function testing valuable in this population. 3

Approximately one-third of patients presenting with acute cough are misdiagnosed with acute bronchitis when they actually have acute asthma, particularly if there have been at least two similar episodes in the past 5 years. 1

Common Pitfalls to Avoid

The Purulent Sputum Fallacy

Purulent sputum does NOT indicate bacterial infection or need for antibiotics. 3, 1

• Purulence occurs when inflammatory cells or sloughed mucosal epithelial cells are present
• This can result from either viral or bacterial infection
• Notably absent from all validated pneumonia prediction rules is the presence of purulent sputum 3

Transient Bronchial Hyperresponsiveness

Many patients with acute bronchitis develop transient bronchial hyperresponsiveness that mimics asthma but typically resolves after 2-3 weeks, occasionally lasting up to 2 months. 3, 1

• Avoid diagnosing chronic asthma based on acute cough illness <3 weeks duration 3
• Reserve evaluation for possible chronic asthma or cough-variant asthma for patients with cough lasting >3 weeks 3

Duration of Cough

Prolonged cough alone (even up to 3 weeks) is NOT an indication for antibiotics, as multiple randomized controlled trials demonstrate that antibiotics do not reduce cough duration in uncomplicated acute bronchitis. 1

Management Approach

Symptomatic Treatment (Both URTI and Acute Bronchitis)

Analgesics (acetaminophen or ibuprofen) for sore throat, chest discomfort, and fever 1

Pseudoephedrine for nasal congestion if present 1

Adequate hydration and rest 1

For persistent bothersome cough beyond 3-5 days, inhaled ipratropium bromide is the first-line cough suppressant (Grade A recommendation) 1

• Benzonatate and other peripheral/central cough suppressants should NOT be prescribed due to limited efficacy 1
• Antihistamines alone are NOT effective for URI symptoms 1

Antibiotic Stewardship

Antibiotics should NOT be prescribed for uncomplicated URTI or acute bronchitis, as they are predominantly viral and antibiotic treatment does not improve outcomes, reduce symptom duration, or prevent complications. 1, 5

Viruses cause more than 90% of acute bronchitis cases, and fewer than 10% have a bacterial etiology. 1

Antibiotics provide only minimal benefit (reducing cough by about half a day) while causing adverse effects including allergic reactions, nausea, vomiting, and Clostridium difficile infection. 5

Expected Clinical Course

Symptoms typically peak at days 3-6 and should begin improving thereafter 1

Most uncomplicated viral URIs resolve within 5-7 days, though cough may persist for up to 3 weeks (post-infectious cough) 1

Red Flags Requiring Re-evaluation

Patients should return if: 1, 2

• Symptoms persist >10 days without improvement
• Symptoms worsen after initial improvement
• New concerning symptoms develop (focal chest findings, significant dyspnea)

Microbiological Testing

In primary care, microbiological tests such as cultures and gram stains are NOT recommended for routine LRTI evaluation. 3, 2

Biomarkers to assess bacterial pathogens are not recommended in primary care settings. 3, 2