What are the diagnosis and treatment guidelines for pneumonia according to Clinical Practice Guidelines (CPG)?

Community-Acquired Pneumonia: Diagnosis and Treatment Guidelines

Diagnosis

Community-acquired pneumonia is diagnosed by the presence of acute respiratory symptoms (fever, cough, dyspnea) plus radiographic confirmation of an infiltrate on chest X-ray or auscultatory findings consistent with pneumonia. 1, 2

Clinical Presentation

• At least 2 of the following signs/symptoms are required: temperature >38°C or ≤36°C, new or worsened cough with or without sputum, dyspnea, chest discomfort, rigors, sweats, or leukocyte count <4000/μL or >10,000/μL 1, 3
• Nonspecific symptoms commonly include fatigue, myalgias, abdominal pain, anorexia, and headache 1
• Clinical characteristics alone cannot reliably establish a specific etiological diagnosis—the traditional "typical" versus "atypical" classification has limited clinical value 2

Diagnostic Testing Strategy

For outpatients with non-severe CAP, routine diagnostic testing (sputum cultures, blood cultures, urine antigens) is NOT recommended. 1, 2

For hospitalized patients with non-severe CAP:

• Obtain blood cultures prior to antibiotic administration 1
• Sputum Gram stain and culture only if a high-quality specimen can be rapidly processed 4
• Do NOT routinely test urine for pneumococcal antigen 1

For severe CAP (ICU admission, septic shock, or mechanical ventilation):

• Obtain pretreatment sputum cultures 1, 4, 2
• Obtain blood cultures prior to antibiotics 1
• Obtain urine antigens for pneumococcus AND Legionella 4, 2
• Test for COVID-19 and influenza when these viruses are circulating in the community 3

Critical Diagnostic Pitfall

Do NOT delay antibiotic administration while pursuing diagnostic testing—empiric therapy must begin immediately upon diagnosis. 4, 2 Blood cultures are associated with increased length of stay and antibiotic duration when false-positive results occur, but remain important in severe disease where covering less-common pathogens is critical 1

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Severity Assessment and Site of Care Decision

Use the Pneumonia Severity Index (PSI) or CURB-65 score as an adjunct to clinical judgment to determine hospitalization need. 1, 4, 2

Severe CAP Criteria (2007 IDSA/ATS)

Patients meeting ANY of the following criteria require ICU-level care: 1

• Septic shock requiring vasopressors
• Respiratory failure requiring mechanical ventilation

Use the 2007 IDSA/ATS severe CAP criteria over other severity scores because they are composed of readily available parameters and demonstrate superior accuracy. 1 Patients transferred to ICU after initial ward admission experience higher mortality than those directly admitted to ICU, suggesting that mis-triage contributes to worse outcomes 1

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Empiric Antibiotic Treatment

Initiate empiric antibiotics immediately based on severity and risk factors, without delaying for diagnostic testing. 4, 2

Healthy Outpatients WITHOUT Comorbidities

First-line options (in order of preference): 1

• Amoxicillin 1 g three times daily (strong recommendation)
• Doxycycline 100 mg twice daily (conditional recommendation)
• Macrolide (azithromycin 500 mg day 1, then 250 mg daily OR clarithromycin 500 mg twice daily) ONLY if local pneumococcal macrolide resistance is <25% (conditional recommendation)

Outpatients WITH Comorbidities

Comorbidities include: chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; or asplenia 1

Combination therapy (strong recommendation): 1

• Amoxicillin/clavulanate 500 mg/125 mg three times daily OR 875 mg/125 mg twice daily OR 2,000 mg/125 mg twice daily
• OR cephalosporin (cefpodoxime 200 mg twice daily OR cefuroxime 500 mg twice daily)
• PLUS macrolide (azithromycin 500 mg day 1, then 250 mg daily OR clarithromycin 500 mg twice daily)

Alternative: Same β-lactam plus doxycycline 100 mg twice daily (conditional recommendation) 1

Hospitalized Patients with Non-Severe CAP

β-lactam plus macrolide combination therapy (strong recommendation): 4, 3

• Ceftriaxone PLUS azithromycin is the most commonly used regimen 3
• Minimum treatment duration is 3 days with clinical stability required before discontinuation 2, 3

Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin or moxifloxacin) 1

Severe CAP (ICU Admission)

β-lactam plus macrolide combination has STRONGER evidence than β-lactam plus fluoroquinolone. 1, 2 This represents a key change from the 2007 guidelines where both combinations were given equal weighting 1

Recommended regimen: 4, 2

• β-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam)
• PLUS macrolide (azithromycin or clarithromycin)

Coverage for Resistant Pathogens

Add MRSA coverage if: 2

• Prior MRSA infection (especially pneumonia)
• Recent hospitalization with IV antibiotics
• High local MRSA prevalence

Add Pseudomonas aeruginosa coverage if: 2

• Prior Pseudomonas infection
• Structural lung disease (bronchiectasis)
• Recent hospitalization with IV antibiotics

Critical Update: The 2019 guidelines recommend ABANDONING the healthcare-associated pneumonia (HCAP) category. Instead, use validated risk factors and local epidemiology to determine need for resistant pathogen coverage, with emphasis on de-escalation if cultures are negative 1

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Treatment Duration and Adjunctive Therapy

Minimum treatment duration is 5 days for all patients, with clinical stability required before discontinuation. 2 Clinical stability is defined as temperature ≤37.8°C, heart rate ≤100 beats/min, respiratory rate ≤24 breaths/min, systolic blood pressure ≥90 mm Hg, oxygen saturation ≥90%, and ability to maintain oral intake 1

Corticosteroids

Do NOT routinely use corticosteroids in CAP. 2 However, corticosteroids may be considered in two specific scenarios:

• Refractory septic shock 2
• Severe CAP (systemic corticosteroids within 24 hours may reduce 28-day mortality) 3

Procalcitonin

Do NOT use procalcitonin to determine need for initial antibacterial therapy. 1 This represents a new recommendation in the 2019 guidelines 1

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Follow-Up and Monitoring

Do NOT obtain routine follow-up chest radiographs in patients who achieve clinical stability. 2 However, consider lung cancer screening if the patient meets eligibility criteria (age 50-80 years, 20 pack-year smoking history, current smoker or quit within 15 years) 2

Key Antibiotic Safety Considerations

Azithromycin warnings (FDA): 5

• QT prolongation and risk of torsades de pointes—use caution in patients with known QT prolongation, bradyarrhythmias, uncompensated heart failure, or concurrent use of QT-prolonging drugs
• Hepatotoxicity—discontinue immediately if signs of hepatitis occur
• Clostridium difficile-associated diarrhea—consider in all patients with diarrhea following antibiotic use

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Common Pitfalls to Avoid

• Never delay antibiotics for diagnostic testing 4, 2
• Do not rely on sputum Gram stain alone to guide initial therapy 4
• Do not use acute-phase reactants as sole determinants to distinguish viral from bacterial CAP 4
• Do not assume all hospitalized patients need broad-spectrum coverage—use validated risk factors for resistant pathogens 1, 2
• Remember that up to 50% of CAP cases have no identified pathogen even with extensive testing, and up to 40% of identified cases are viral 2, 3