What is the approach to diagnosis and management of an adult patient with no significant past medical history presenting with symptoms suggestive of asthma or pneumonia?

Distinguishing Asthma from Pneumonia in Adults Without Significant Medical History

Initial Clinical Assessment

The primary goal is to rule out pneumonia first, as it carries significant morbidity and mortality when untreated, whereas acute bronchitis is typically self-limited. 1

Key Clinical Findings That Suggest Pneumonia Over Asthma or Bronchitis

If ANY of the following vital sign abnormalities or physical exam findings are present, pneumonia is likely and chest radiography is indicated:

• Heart rate >100 beats/min 1
• Respiratory rate >24 breaths/min 1
• Oral temperature >38°C 1
• Focal consolidation on chest exam (rales, egophony, or fremitus) 1

If ALL four of these findings are absent, the likelihood of pneumonia is sufficiently low that chest radiography may not be necessary. 1

Important Caveat About Sputum

Purulent sputum does NOT distinguish pneumonia from acute bronchitis—it can occur with viral or bacterial infections and should not guide antibiotic decisions. 1

Distinguishing Asthma from Acute Bronchitis

Timing Is Critical

• Acute cough <2-3 weeks duration: Asthma is difficult to establish because transient bronchial hyperresponsiveness occurs commonly with acute bronchitis and typically resolves within 2-3 weeks (occasionally up to 2 months). 1

• Persistent cough >3 weeks: Consider cough-variant asthma, especially if the cough worsens at night or after cold/exercise exposure. 1

Clinical Features Suggesting Asthma

Consider underlying asthma (not just acute bronchitis) when ≥2 of the following are present:

• Wheezing 2
• Prolonged expiration 2
• Smoking history 2
• History of allergy 2
• Female sex 2

Up to 45% of patients with acute cough >2 weeks actually have underlying asthma or COPD. 2

Diagnostic Approach Algorithm

Step 1: Assess for Pneumonia

1. Check vital signs and perform focused chest examination looking for the four key findings above 1

2. If any abnormality present: Obtain chest radiograph to confirm or exclude pneumonia 1

3. If chest radiograph confirms pneumonia: Initiate antibiotic therapy immediately 1, 2

Step 2: If Pneumonia Excluded, Assess for Asthma vs Bronchitis

1. Duration <3 weeks AND no severe airflow obstruction: Diagnose as acute bronchitis; limit evaluation for chronic asthma 1

2. Duration >3 weeks OR recurrent episodes: Consider pulmonary function testing or methacholine challenge to diagnose asthma 1

3. Presence of wheezing with ≥2 risk factors listed above: Consider lung function testing even if duration <3 weeks 2

Management Based on Diagnosis

If Pneumonia Confirmed

• Initiate antibiotics promptly (ideally within 4 hours if hospitalized) 3
• First-line outpatient therapy: Amoxicillin or tetracycline 1
• Alternative if penicillin allergy: Macrolide (azithromycin, clarithromycin) or fluoroquinolone in areas with low pneumococcal macrolide resistance 1

If Asthma Diagnosed

• Initiate inhaled short-acting beta-agonists (albuterol) for acute symptoms 4, 5
• Add inhaled anticholinergics for moderate-to-severe exacerbations 5
• Systemic corticosteroids for acute exacerbations 5
• Controller therapy (inhaled corticosteroids) for persistent asthma 6

If Acute Bronchitis Without Pneumonia

Antibiotics are NOT routinely indicated unless the patient has serious comorbidity such as:

• Selected COPD exacerbations 1, 2
• Cardiac failure 1, 2
• Insulin-dependent diabetes 1, 2
• Serious neurological disorder 1, 2

Do NOT prescribe: Cough suppressants, expectorants, mucolytics, antihistamines, inhaled corticosteroids, or bronchodilators for uncomplicated acute bronchitis 1

Laboratory Values

Limited Role in Differentiation

• No serum markers can distinguish pneumonia from acute bronchitis with sufficient accuracy 1
• Sputum analysis is not routinely indicated for acute bronchitis 1
• C-reactive protein (if available): >100 mg/L suggests pneumonia; <20 mg/L (with symptoms >24 hours) makes pneumonia unlikely 2

When Labs Are Helpful

• Leukocytosis may support pneumonia but is not diagnostic 1
• Hypoxemia (oxygen saturation measurement) indicates severe disease requiring hospitalization 3

Critical Pitfalls to Avoid

1. Do not assume purulent sputum = bacterial infection requiring antibiotics 1

2. Do not diagnose asthma during acute illness <3 weeks duration without recognizing that bronchial hyperresponsiveness may be transient 1

3. Do not delay chest radiography in patients with abnormal vital signs or focal findings—pneumonia requires prompt treatment 1

4. Do not prescribe antibiotics for uncomplicated acute bronchitis in otherwise healthy adults 1

5. In elderly patients, maintain high suspicion for pneumonia as they may present with atypical symptoms (confusion, falls) without fever 1, 2

Follow-Up Monitoring

• Patients should return if symptoms persist >3 weeks 1
• Clinical improvement expected within 3 days of antibiotic therapy for pneumonia 1, 2
• Seriously ill patients require reassessment within 2 days 1, 2