What is the appropriate diagnostic and treatment approach for an adult patient with respiratory symptoms, such as cough, fever, or shortness of breath, and no significant underlying medical conditions?

Diagnostic and Treatment Approach for Adult Respiratory Symptoms

For an adult with respiratory symptoms (cough, fever, shortness of breath) and no significant comorbidities, obtain a chest radiograph and pulse oximetry immediately to establish or exclude pneumonia, as clinical features alone are insufficient for diagnosis. 1

Initial Clinical Assessment

Mandatory Screening and Imaging

• Pulse oximetry screening is required for all patients to detect unsuspected hypoxemia and support the presence of pneumonia even when clinical signs are not obvious 1
• Chest radiography is mandatory to establish the diagnosis of pneumonia and differentiate it from acute bronchitis, which presents with similar symptoms but does not require antibiotics 1
• Physical examination findings (rales, bronchial breath sounds) are less sensitive and specific than chest radiographs and cannot reliably exclude pneumonia 1

Key Physical Examination Findings

• Dull percussion note and pleural rub are highly specific for pneumonia when present, though their absence does not exclude the diagnosis 2
• Inspiratory crackles occur in approximately 81% of pneumonia cases and represent sudden opening of collapsed alveoli filled with inflammatory exudate 3
• Diminished breath sounds in focal areas indicate consolidation and reduced air movement 3, 2
• New focal chest signs increase pneumonia probability from 5-10% to 39% 2

Diagnostic Algorithm

When Pneumonia is Suspected (fever + respiratory symptoms + abnormal exam)

1. Obtain chest radiograph immediately - required to confirm infiltrate and establish diagnosis 1
2. Measure C-reactive protein (CRP) to strengthen diagnostic certainty:
   • CRP >30 mg/L significantly increases likelihood of pneumonia 3
   • CRP <10 mg/L in absence of dyspnea and daily fever decreases likelihood 3
3. Do NOT routinely order procalcitonin - adds no diagnostic value beyond symptoms, signs, and CRP 3

When Acute Viral Syndrome is More Likely (fever + systemic symptoms WITHOUT respiratory focus)

• Classic triad includes: acute fever, systemic symptoms (fatigue, body aches, chills), and notably the absence of prominent respiratory symptoms 4
• This presentation helps exclude bacterial pneumonia or severe respiratory infection 4
• Supportive care is appropriate: rest, hydration, antipyretics 4

Microbiological Testing Indications

Order respiratory pathogen testing only when results would change management 1:

• Haemoptysis present 1
• Prominent systemic illness suggesting unusual pathogens 1
• Recent travel or endemic exposure (fungi, tuberculosis) 1
• Suspected influenza during flu season (enables antiviral therapy) 5

For influenza specifically:

• Rapid antigen testing has high false-negative rates but enables early screening 1
• Nucleic acid detection (PCR) is preferred for respiratory virus identification 1
• Oseltamivir 75 mg twice daily for 5 days reduces illness duration by 1.3 days when started within 48 hours of symptom onset 5

Treatment Decisions

Empirical Antibiotics - When to Prescribe

Start empirical antibiotics when:

• Chest radiograph confirms infiltrate AND abnormal vital signs present 3
• Clinical pneumonia suspected with abnormal breath sounds and vital signs, especially if imaging unavailable 3

Do NOT prescribe antibiotics when:

• Normal vital signs AND normal lung examination 3
• Acute bronchitis suspected (cough without infiltrate) 1
• Viral respiratory panel positive for virus (reduces antibiotic use appropriately) 6

Common Pitfalls to Avoid

• Do not assume chest X-ray sensitivity is perfect: CT may detect pneumonia when radiography is negative, though clinical significance is unclear 1
• Wheezing, cough, or rhonchi alone do not increase pneumonia likelihood on chest radiograph 3
• Elderly patients may have atypical presentations with absent or altered physical findings despite radiographic pneumonia 3
• Do not dismiss the possibility of delayed sepsis - monitor for red flags including persistent hypotension, altered mental status, or respiratory distress 4
• Even minor wounds can become portals for bacterial infection causing systemic symptoms - evaluate carefully 4

Monitoring and Follow-up

Patients require immediate medical attention if 4:

• Recurrence of high-grade fever
• Development of new respiratory symptoms
• Signs of clinical deterioration

For initially negative chest radiographs in toxic-appearing patients: treat presumptively with antibiotics and repeat imaging in 24-48 hours 1