New Onset Cough with Basilar Crackles: Diagnostic Workup
Order a chest X-ray immediately, measure vital signs including temperature and respiratory rate, and obtain C-reactive protein (CRP) if available—this presentation of new cough with basilar crackles is highly suggestive of pneumonia and requires prompt imaging to confirm consolidation. 1
Initial Diagnostic Approach
Immediate Orders
Chest radiography (posteroanterior and lateral views): This is the essential first test when crackles are present with new cough, as the combination of breathlessness, crackles, and diminished breath sounds significantly increases pneumonia likelihood 1, 2
Vital signs assessment: Specifically measure temperature (fever ≥38°C), respiratory rate (tachypnea >25/min), heart rate, and oxygen saturation 1
C-reactive protein (CRP): A CRP >30 mg/L combined with crackles and fever substantially strengthens the diagnosis of pneumonia, while CRP <10 mg/L makes pneumonia less likely 1, 2
Clinical Assessment Points
The presence of crackles at the lung bases combined with new cough creates a high pretest probability for pneumonia, particularly when accompanied by: 1, 2
- Fever ≥38°C
- Dyspnea or breathlessness
- Tachypnea (respiratory rate >25/min)
- Absence of runny nose (which would suggest viral upper respiratory infection)
Common pitfall: Do not dismiss this as simple bronchitis or viral illness based solely on the absence of fever—crackles represent pathologic alveolar or airway involvement requiring radiographic confirmation 1
If Chest X-ray Shows Infiltrate/Consolidation
Confirmed Pneumonia Management
Initiate empiric antibiotics according to local community-acquired pneumonia guidelines immediately, even before additional testing if clinical suspicion is high 1, 3
No routine microbiological testing needed in outpatient settings unless results would change therapy (e.g., suspected tuberculosis, treatment failure, or immunocompromised status) 1
Do NOT routinely order procalcitonin—it adds no diagnostic value beyond clinical findings and CRP 1
Severity Assessment
Check for abnormal vital signs that would necessitate hospitalization or closer monitoring: 1
- Respiratory rate >30/min
- Oxygen saturation <90% on room air
- Systolic blood pressure <90 mmHg
- Altered mental status (in elderly patients ≥70 years)
If Chest X-ray is Normal or Equivocal
Consider Alternative Diagnoses
When crackles are present but imaging is negative or non-diagnostic, the differential broadens: 1
Early pneumonia: Repeat chest X-ray in 24-48 hours if clinical suspicion remains high, as infiltrates may not be visible initially 1
Influenza with secondary bacterial infection: If within 48 hours of symptom onset and during flu season, consider rapid influenza testing and initiate antivirals per CDC guidance—this may decrease antibiotic use and hospitalization 1
Postinfectious cough with transient crackles: If preceded by viral upper respiratory infection within past 3 weeks, crackles may represent residual airway inflammation rather than pneumonia 1, 4
Bronchiectasis or interstitial lung disease: Consider high-resolution CT if crackles persist, especially if accompanied by chronic productive cough or progressive dyspnea 1
Management When Imaging Cannot Be Obtained
If chest X-ray is unavailable and clinical suspicion for pneumonia is high (crackles + fever + dyspnea + elevated CRP), empiric antibiotics are justified per local guidelines rather than delaying treatment 1
Critical Red Flags Requiring Immediate Advanced Evaluation
Do not attribute crackles to benign causes if any of the following are present: 1, 4
- Hemoptysis (any amount)
- Weight loss or night sweats
- Persistent fever despite initial treatment
- Progressive dyspnea
- Immunocompromised state
These warrant immediate chest imaging, possible CT scan, and consideration of tuberculosis, malignancy, or opportunistic infection 1, 3
What NOT to Order Initially
Avoid routine procalcitonin: No evidence it improves diagnostic accuracy beyond clinical assessment and CRP 1
Do not order CT chest as first-line imaging: Reserve for cases where chest X-ray is non-diagnostic but clinical suspicion remains high, or when alternative diagnoses like interstitial lung disease or bronchiectasis are suspected 1
Do not order antibiotics without attempting to confirm diagnosis when vital signs and lung exam are normal—routine antibiotic use in this setting is explicitly not recommended 1