Distinguishing Asthma from Pneumonia in Adults

Initial Assessment and Diagnosis

The American College of Chest Physicians recommends that 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, 2
Patients with vital sign abnormalities, such as heart rate >100 beats/min, respiratory rate >24 breaths/min, oral temperature >38°C, or focal consolidation on chest exam, are likely to have pneumonia and should undergo chest radiography 1, 2
If all four of these findings are absent, the likelihood of pneumonia is sufficiently low that chest radiography may not be necessary 1, 2
The American College of Emergency Physicians suggests that purulent sputum does not distinguish pneumonia from acute bronchitis and should not guide antibiotic decisions 3, 1

The American College of Chest Physicians recommends that acute cough <2-3 weeks duration is difficult to establish as asthma because transient bronchial hyperresponsiveness occurs commonly with acute bronchitis and typically resolves within 2-3 weeks 3, 1
Persistent cough >3 weeks may indicate cough-variant asthma, especially if the cough worsens at night or after cold/exercise exposure 3
The presence of wheezing with ≥2 risk factors, such as smoking history, history of allergy, or female sex, suggests underlying asthma 4

The American Thoracic Society recommends initiating antibiotics promptly for pneumonia, ideally within 4 hours if hospitalized 8
First-line outpatient therapy for pneumonia is amoxicillin or tetracycline, with alternative options for patients with penicillin allergy 7
The American College of Radiology suggests that chest radiography is necessary to confirm or exclude pneumonia in patients with abnormal vital signs or focal findings 5, 2
The European Respiratory Society recommends that antibiotics are not routinely indicated for acute bronchitis unless the patient has serious comorbidity, such as COPD exacerbations, cardiac failure, insulin-dependent diabetes, or serious neurological disorder 7, 4

The American College of Chest Physicians recommends that no serum markers can distinguish pneumonia from acute bronchitis with sufficient accuracy 1, 2
Sputum analysis is not routinely indicated for acute bronchitis, but C-reactive protein may be helpful in distinguishing pneumonia from acute bronchitis 1, 2, 4
Patients should return if symptoms persist >3 weeks, and clinical improvement is expected within 3 days of antibiotic therapy for pneumonia 7, 4
Seriously ill patients require reassessment within 2 days 7, 4