What is the pictorial representation of pneumonia classification?

Pneumonia Classification Systems

I cannot provide a flowchart or pictorial representation in this text-based format, but I can describe the key classification frameworks that would form the basis of such diagrams.

Classification by Setting of Acquisition

Pneumonia is primarily classified by where it was acquired, which fundamentally determines pathogen likelihood and treatment approach. 1

• Community-Acquired Pneumonia (CAP): Infection acquired outside healthcare settings 1, 2
• Hospital-Acquired Pneumonia (HAP): Develops ≥48 hours after hospital admission 1, 3
• Ventilator-Associated Pneumonia (VAP): Develops ≥48 hours after endotracheal intubation 3
• Healthcare-Associated Pneumonia (HCAP): The ATS/IDSA now recommend abandoning this category entirely because it had poor positive predictive value for multidrug-resistant organisms and led to inappropriate broad-spectrum antibiotic overuse 1, 3

Important Caveat

Instead of using HCAP classification, clinicians should assess individual risk factors for MDR organisms: antimicrobial therapy in preceding 90 days, hospitalization ≥5 days, high local antibiotic resistance rates, hospitalization for ≥2 days in preceding 90 days, nursing home residence, home infusion therapy, chronic dialysis within 30 days, home wound care, family member with MDR pathogen, or immunosuppression 1

Classification by Severity (Site-of-Care Decision)

The severity assessment is the single most important clinical decision, directly affecting hospitalization, testing intensity, antibiotic selection, and costs. 4, 1

CURB-65 Score (Simplified Severity Tool)

Each criterion = 1 point 5:

• Confusion (new onset)
• Urea >7 mmol/L (BUN >19 mg/dL)
• Respiratory rate ≥30/min
• Blood pressure: systolic <90 mmHg or diastolic ≤60 mmHg
• Age ≥65 years

Treatment recommendations based on CURB-65 5:

• Score 0-1: Outpatient treatment (mortality 0.1-0.6%) 4
• Score 2: Consider hospitalization or brief observation (mortality 0.9-2.8%) 4
• Score ≥3: Hospitalization required (mortality 9.3-31.1%) 4

Pneumonia Severity Index (PSI) - Five Risk Classes

The PSI stratifies patients into 5 classes based on age, comorbidities, and clinical parameters 4, 5:

• Class I: Age <50 years with no high-risk comorbidities (mortality 0.1%) 4
• Class II: <70 total points (mortality 0.6%) 4
• Class III: 71-90 points (mortality 0.9-2.8%) 4
• Class IV: 91-130 points (mortality 8.2-9.3%) 4
• Class V: >130 points (mortality 27.0-31.1%) 4

Site-of-care recommendations 4:

• Classes I-II: Outpatient treatment
• Class III: Brief observation or outpatient with close follow-up
• Classes IV-V: Hospitalization required

Severe CAP Requiring ICU Admission

Severe pneumonia is defined by presence of ≥1 major criterion OR ≥3 minor criteria 6:

Major criteria 6:

• Mechanical ventilation required
• Septic shock requiring vasopressors

Minor criteria 6:

• Respiratory rate ≥30/min
• PaO₂/FiO₂ ratio <250
• Multilobar infiltrates
• Confusion/disorientation
• Uremia (BUN ≥20 mg/dL)
• Leukopenia (WBC <4,000/μL)
• Thrombocytopenia (platelets <100,000/μL)
• Hypothermia (core temperature <36°C)
• Hypotension requiring aggressive fluid resuscitation

Alternative simplified rule for severe CAP: 2 of 3 minor criteria (systolic BP <90 mmHg, multilobar involvement, PaO₂/FiO₂ <250) OR 1 of 2 major criteria had 78% sensitivity and 94% specificity 6

Classification by Etiology (Limited Clinical Utility)

The traditional "typical" versus "atypical" classification has limited clinical value and cannot reliably establish etiologic diagnosis based on clinical features alone. 1, 2

Common Pathogens by Setting

Community-acquired (hospitalized patients) 4:

• Streptococcus pneumoniae: 11-39% (varies by region)
• Mycoplasma pneumoniae: 4-15%
• Chlamydophila pneumoniae: 3-13%
• Viruses (all): 9-13%
• Legionella spp: 4-8%
• Haemophilus influenzae: 4-10%

Severe CAP (ICU patients) 4:

• S. pneumoniae: 22% (UK and Europe)
• Legionella spp: 6-18%
• Staphylococcus aureus: 7-9%
• Gram-negative enteric bacilli: 2-9%

Pediatric Classification (Ages 2-59 months)

WHO/IMCI 2014 classification divides pediatric pneumonia into two categories 4:

1. Pneumonia: Cough or difficulty breathing WITH tachypnea or lower chest wall indrawing → Outpatient oral amoxicillin 4

2. Severe pneumonia: Pneumonia PLUS any general danger sign, OR cough/difficulty breathing → Referral and parenteral antibiotics 4

Hospitalization criteria for children 1:

• All infants <6 months of age
• Oxygen saturation <92% on room air
• Signs of respiratory distress
• Significant comorbidities
• Dehydration, vomiting, or inability to take oral medication

Common Pitfalls to Avoid

• Never rely on a single severity score without clinical judgment: Scores may underestimate risk in immunocompromised patients or those with rapidly progressive disease 5
• Do not use HCAP classification to automatically prescribe broad-spectrum antibiotics: This leads to overtreatment; use validated individual MDR risk factors instead 1
• Avoid delaying antibiotics for diagnostic studies in unstable patients: Delays increase mortality 1
• Do not assume clinical features can determine etiology: Clinical presentation cannot reliably distinguish bacterial from viral or typical from atypical pathogens 1, 2
• Reassess severity regularly during hospitalization: Initial classification may change as disease evolves 5