Risk Stratification of Community-Acquired Pneumonia in the Philippines
In the Philippines, community-acquired pneumonia should be risk stratified using CURB-65 as the primary tool for initial site-of-care decisions, supplemented by the Pneumonia Severity Index (PSI) when more detailed mortality prediction is needed, and the 2007 IDSA/ATS severe CAP criteria specifically for ICU admission decisions. 1, 2
Primary Risk Stratification Tool: CURB-65
CURB-65 is the preferred initial assessment tool due to its simplicity and practicality in emergency settings, requiring only one laboratory test (urea/BUN) that is readily available in most Philippine hospitals. 2
CURB-65 Components (1 point each):
- Confusion (new onset disorientation)
- Urea nitrogen >7 mmol/L (>19.6 mg/dL) or BUN >20 mg/dL
- Respiratory rate ≥30 breaths/minute
- Blood pressure: systolic <90 mmHg or diastolic ≤60 mmHg
- Age ≥65 years 1, 2
CURB-65 Risk Stratification and Management:
Score 0-1 (Low Risk):
- Mortality risk: 0.7-2.1% 2
- Management: Consider outpatient treatment 1, 2
- These patients can safely return to work/normal activities sooner than hospitalized patients 1
Score 2 (Intermediate Risk):
- Mortality risk: 9.2% 2
- Management: Consider short hospital stay or supervised outpatient treatment with close follow-up 2
- Clinical judgment is particularly important in this group, as social factors and comorbidities may necessitate admission despite the score 2
Score 3 (High Risk):
Score 4-5 (Very High Risk):
Alternative Tool: CRB-65 for Resource-Limited Settings
In Philippine settings where laboratory testing is unavailable (rural health centers, remote areas), use CRB-65, which omits the urea measurement and scores 0-4 points. 2, 3 This simplified version maintains comparable predictive accuracy while being more accessible in resource-limited environments. 2, 3
Secondary Tool: Pneumonia Severity Index (PSI)
The PSI provides more detailed mortality prediction using 20 variables including demographics, comorbidities, vital signs, laboratory values, and radiographic findings. 4, 5
PSI Risk Classes and Management:
- Class I-II: Mortality ≤0.7%; outpatient treatment 1, 4
- Class III: Mortality 0.9-2.8%; observation unit or short hospitalization 1, 4
- Class IV: Mortality 8%; inpatient treatment 4
- Class V: Mortality 35%; inpatient treatment 4
When to use PSI: The PSI is slightly better at identifying the lowest-risk patients who can be safely treated as outpatients, but its complexity (20 variables) makes it less practical for initial emergency assessment. 6, 5 Use PSI when more detailed risk stratification is needed or when CURB-65 results are borderline. 1
ICU Admission Criteria: 2007 IDSA/ATS Severe CAP Criteria
Critical limitation: CURB-65 alone performs poorly for predicting ICU needs (sensitivity only 78.4%). 2 Therefore, use the IDSA/ATS severe CAP criteria specifically for ICU triage decisions. 1, 2
Major Criteria (Either one requires ICU admission):
- Septic shock requiring vasopressors 1, 2
- Acute respiratory failure requiring intubation and mechanical ventilation 1, 2
Minor Criteria (≥3 requires ICU or high-level monitoring unit):
- Respiratory rate ≥30/min
- PaO₂/FiO₂ ratio ≤250
- Multilobar infiltrates
- Confusion/disorientation
- Uremia (BUN ≥20 mg/dL)
- Leukopenia (WBC <4,000 cells/mm³)
- Thrombocytopenia (platelets <100,000/mm³)
- Hypothermia (core temperature <36°C)
- Hypotension requiring aggressive fluid resuscitation 1, 2
Clinical Implementation Algorithm
Step 1: Calculate CURB-65 score on all CAP patients presenting to emergency departments or clinics. 1, 2
Step 2: Apply initial site-of-care decision:
- Score 0-1: Consider outpatient treatment
- Score 2: Clinical judgment required; consider patient-specific factors
- Score ≥3: Hospital admission required 2
Step 3: For hospitalized patients, immediately assess for ICU criteria using IDSA/ATS severe CAP criteria. 1, 2
Step 4: If PSI calculation is feasible and CURB-65 results are borderline (especially score 2), use PSI for additional risk stratification. 1, 6
Critical Caveats and Pitfalls
CURB-65 Limitations:
- Underestimates severity in young patients (<65 years) with severe respiratory failure who may have low scores despite significant physiologic derangement 2
- May overestimate risk in elderly patients with multiple comorbidities but without true pneumonia severity 2
- Age bias: Heavily weights age, requiring much more severe physiologic abnormalities in young patients to achieve the same risk class 1
Factors That Override Low Scores (Require Admission Despite CURB-65 0-1):
- Inability to maintain oral intake
- Homelessness or lack of social support
- Psychiatric illness affecting medication adherence
- Substance abuse
- Cognitive impairment affecting self-care
- Exacerbation of underlying comorbidities (COPD, heart failure, diabetes)
- HIV or other immunocompromising conditions
- Prior splenectomy
- Failure of outpatient therapy 1, 2
Timing Considerations:
- Delayed ICU admission increases mortality: Patients transferred to ICU after initial ward admission have higher mortality than those directly admitted from emergency departments. 1 Therefore, promptly evaluate all patients with CURB-65 ≥3 for ICU criteria. 2
- Antibiotic timing matters: Aim for antibiotic administration within 6 hours of emergency department presentation, as delays worsen outcomes. 1
Enhanced Assessment Tools
Incorporate pulse oximetry and point-of-care lactate as part of immediate evaluation, as postponing oxygenation assessment adversely affects outcomes. 2 These adjuncts help identify patients with severe respiratory compromise who may have deceptively low CURB-65 scores. 2
Key Principle
Use these scoring systems as adjuncts to clinical judgment, never as sole determinants. 1, 4 Patients may have rare conditions not captured by these rules (severe neuromuscular disease, prior splenectomy) that increase poor prognosis risk. 1 The "art of medicine" remains essential in site-of-care decisions. 1