CLINICAL ACTIONS:

Community-acquired pneumonia (CAP), by definition, is pneumonia acquired outside a hospital. A joint guideline (2019) from the American Thoracic Society/IDSA addresses diagnosis, management and follow-up. The focus of this document is on non-immunocompromised individuals (e.g., those without inherited or acquired immune deficiency or drug-induced neutropenia, those actively receiving cancer chemotherapy, HIV with suppressed CD4 counts or transplant recipients).

Diagnosis (CDC)

• History
  • Abrupt onset of fever, chills or rigors
    • Typically, a single rigor and repeated shaking chills are not commonly seen
    • Older individuals may not mount a fever
  • Pleuritic chest pain
  • Cough productive of mucopurulent, rusty sputum
• Clinical exam
  • Dyspnea
  • Tachypnea or tachycardia
  • Hypoxia
  • Malaise or weakness
  • Nausea, vomiting and headache may occur, but is less common
  • Auscultation
    • Crackles
    • Dullness to percussion, egophony (voiced sounds more audible than usual) may signal consolidation
• Lab
  • Elevated WBC
• Imaging
  • Guideline recommends radiographic confirmation with plain chest film (evidence of infiltrate) due to inaccuracy of clinical findings  

Decision to Treat as Outpatient vs Inpatient

• In addition to clinical judgment, the Pneumonia Severity Index (PSI) can be used to determine treatment setting (see ‘learn more’ for calculators)
  • PSI is considered superior to CURB-65 based on RCTs although CURB-65 has the benefit of simplicity and ease of use  
  • The score predicts probability of mortality  
• PSI is a points-based system that uses the following features
  • Age | Comorbidities | Abnormal physical findings (e.g., respiratory rate of ≥30 or a temperature of ≥40 degrees C) | Abnormal labs (e.g., pH <7.35, a BUN ≥30 mg per dL (11 mmol per liter) or a sodium concentration <130 mmol per liter

Tests at Time of Diagnosis if Managed in the Outpatient Setting

• Gram stain and culture of lower respiratory secretions: Not recommended
• Blood cultures: Not recommended
• Legionella and Pneumococcal Urinary Antigen Testing: Not recommended (unless epidemiologic reasons, i.e., recent outbreak)
• Influenza: Recommended during periods of high influenza activity | Consider during periods of low influenza activity  
  • Use rapid influenza molecular assay (i.e., influenza nucleic acid amplification test) vs rapid influenza diagnostic test (i.e., antigen test)
  • Patient tests positive: Treat with anti-influenza medication (e.g., oseltamivir) independent of length of time of illness before diagnosis
  • Treat with standard antibacterial treatment (see below) for patients with clinical and radiographic evidence of CAP
•   Serum Procalcitonin: Should not be used to determine whether to withhold antibiotics
  • Some studies have indicated that serum procalcitonin could discriminate between viral and bacterial infection (biomarker levels higher in bacterial disease)
  • No clinical threshold has been established, with sensitivities ranging from 38% to 91%

Note: The American Thoracic Society has published guidelines regarding nucleic acid-based testing for viral pathogens in the setting of CAP

• Outpatients with suspected CAP
  • Recommendation against testing for respiratory samples for viral pathogen other than influenza (conditional recommendation, very-low-quality evidence)
• Hospitalized patients with suspected CAP
  • Recommendation against routine testing other for influenza unless severe CAP or immunocompromised (conditional recommendation, very-low-quality evidence)

SYNOPSIS:

Approximately 400,000 hospitalizations from pneumococcal pneumonia occur annually in the US. Pneumococci are responsible for up to 30% of adult CAP, with an incubation period of approximately 1 to 3 days. According the CDC, “the case-fatality rate is 5–7% and may be much higher among elderly persons.” Other bacterial pathogens include Haemophilus influenzae, Mycoplasma pneumoniae, Staphylococcus aureus, Legionella species, Chlamydia pneumoniae, and Moraxella catarrhalis. According the guideline, “The newer multidrug-resistant pathogens, including methicillin-resistant S. aureus (MRSA) and Pseudomonas aeruginosa requires separate treatment options.”

KEY POINTS:

Treatment

No comorbidities or Risk Factors for MRSA or Pseudomonas aeruginosa

• Amoxicillin 1 g three times daily (strong recommendation) or
• Doxycycline 100 mg twice daily (conditional recommendation) or
• Macrolide (conditional recommendations and only in areas with pneumococcal resistance to macrolides <25%): Azithromycin 500 mg on first day then 250 mg daily or clarithromycin 500 mg twice daily or clarithromycin extended release 1,000 mg daily

Outpatient with Comorbidities (can be ‘combination therapy’ or ‘monotherapy’ with no order of preference)

Combination Therapy (Amoxicillin/clavulanate or cephalosporin combined with a macrolide or doxycycline)

• Amoxicillin/clavulanate 500 mg/125 mg three times daily or amoxicillin/clavulanate 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

• A macrolide: Azithromycin 500 mg on first day then 250 mg daily or clarithromycin 500 mg twice daily or extended release 1,000 mg once daily or
• Doxycycline 100 mg twice daily

Monotherapy

• Respiratory fluoroquinolone: Levofloxacin 750 mg daily or
• moxifloxacin 400 mg daily or
• Gemifloxacin 320 mg daily

Note: Comorbidities include: Chronic heart | Lung, liver, or renal disease | Diabetes mellitus | Alcoholism | Malignancy | Asplenia

Duration of Antibiotic Treatment and Follow-Up

• Antibiotic treatment in patients who are improving “should be continued until the patient achieves stability and for no less than a total of 5 days (strong recommendation, moderate quality of evidence)”
• Evidence of clinical stability includes
  • Resolution and stabilization of vital signs
  • Ability to eat
  • Normal mentation
• Need for follow-up chest film
  • In patients who recover within 5 to 7 days, the guideline suggests that routine CXR follow up is not required
  • Based on the literature, patients with lung cancer would have been candidates for routine screening and were generally current or ex-smokers

Learn More – Primary Sources:

Guideline: The American Thoracic Society and Infectious Diseases Society of America provide recommendations for the diagnosis and treatment of adults with community-acquired pneumonia.

American Thoracic Society: Nucleic Acid–based Testing for Noninfluenza Viral Pathogens in Adults
with Suspected Community-acquired Pneumonia

Outpatient vs. Inpatient Treatment of Community-Acquired Pneumonia: PSI and CURB-65 Scoring Models

QXMD PSI Calculator

CDC: Pneumococcal Disease

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