CURB-65 Score for Community-Acquired Pneumonia
CURB-65 is a validated 5-point severity assessment tool that stratifies pneumonia patients by mortality risk and guides site-of-care decisions: scores 0-1 indicate outpatient treatment, score 2 requires hospitalization or intensive home care, and scores ≥3 mandate hospital admission with ICU evaluation. 1
Components and Calculation
CURB-65 assigns one point for each of the following criteria 1, 2:
- Confusion (new onset)
- Urea >19 mg/dL (>7 mmol/L)
- Respiratory rate ≥30 breaths/minute
- Blood pressure: systolic <90 mmHg or diastolic ≤60 mmHg
- Age ≥65 years
The score ranges from 0-5 points, with higher scores indicating greater severity.
Risk Stratification and Mortality
The mortality risk increases directly with score 1, 2:
- Score 0: 0.7-1.1% mortality
- Score 1: 2.1% mortality
- Score 2: 9.2% mortality
- Score 3: 14.5-21% mortality
- Score 4: 40-41.9% mortality
- Score 5: 57-60% mortality
Site-of-Care Decisions
Outpatient Treatment (Score 0-1)
Patients with CURB-65 scores of 0-1 can be safely treated as outpatients with oral antibiotics, as mortality risk is only 0.7-2.1%. 1, 3 The British Thoracic Society recommends considering outpatient management for these low-risk patients 4. However, age ≥65 as the sole criterion should not automatically trigger hospitalization 4.
Hospitalization or Intensive Home Care (Score 2)
A CURB-65 score of 2 carries 9.2% mortality and warrants hospitalization or intensive in-home health services where available. 4, 1 The IDSA/ATS guidelines emphasize that these patients have clinically important physiologic derangements requiring active intervention 4. Clinical judgment is particularly important in this intermediate-risk group 3.
Hospital Admission with ICU Assessment (Score ≥3)
Patients with CURB-65 scores ≥3 require hospital admission and prompt evaluation for ICU care, with mortality ranging from 14.5% to 60%. 1, 3 These patients are at substantially elevated risk and need intensive monitoring 4.
Critical Limitations and Pitfalls
When CURB-65 Underestimates Severity
CURB-65 may dangerously underestimate severity in young patients (<65 years) with severe respiratory failure who lack age points despite significant physiologic derangement. 1, 3 For example, a previously healthy 25-year-old with severe hypotension and tachycardia would score only 1 point, potentially leading to inappropriate outpatient management 4.
Elderly patients with multiple stable comorbidities may have falsely elevated scores without true severity. 1 A 70-year-old with stable chronic conditions but minimal acute illness may score 1-2 points based on age and chronic urea elevation alone 4.
ICU Admission Decisions
For ICU triage, CURB-65 performs poorly with only 78.4% sensitivity for predicting critical care interventions—use the IDSA/ATS severe CAP criteria instead. 1, 5 Direct ICU admission is required for patients with septic shock requiring vasopressors or acute respiratory failure requiring intubation, regardless of CURB-65 score 4, 1.
Admit to ICU or high-level monitoring if ≥3 minor IDSA/ATS criteria are present: respiratory rate ≥30/min, PaO2/FiO2 ratio ≤250, multilobar infiltrates, confusion, uremia, leukopenia, thrombocytopenia, hypothermia, or hypotension requiring aggressive fluid resuscitation 1.
Non-Clinical Factors Requiring Hospitalization
Consider hospitalization despite low CURB-65 scores for 4, 3:
- Inability to maintain oral intake or intractable vomiting
- Homelessness or lack of social support/caregiver
- Severe psychiatric illness or cognitive dysfunction
- Injection drug abuse
- Failure of prior adequate outpatient antibiotic therapy
- Exacerbation of underlying diseases (COPD, heart failure, diabetes) requiring hospital-level care
- Need for supplemental oxygen or pleural effusion drainage
Simplified Alternative: CRB-65
CRB-65 omits the urea measurement and is useful in outpatient settings or resource-limited environments where laboratory testing is unavailable. 4, 1 It uses the same interpretation but with a 0-4 point range 4.
Comparison with Pneumonia Severity Index (PSI)
Both CURB-65 and PSI are comparable in predicting mortality, but CURB-65 is preferred for its simplicity and focus on illness severity rather than just mortality risk. 4 The PSI requires 20 variables including laboratory and radiographic data, making it more complex but similarly effective 1, 6. PSI is primarily designed to identify low-risk patients for outpatient treatment 1, 6.
Implementation Best Practices
Use CURB-65 as an adjunct to clinical judgment, not as the sole determinant for site-of-care decisions. 1, 3 The European Respiratory Society emphasizes that clinical judgment must take priority, with CURB-65 serving to validate rather than replace clinical assessment 4.
Implement CURB-65 as part of a systematic pneumonia care bundle with pulse oximetry and point-of-care lactate for immediate evaluation. 1 Clinical improvement should be expected within 3 days; patients should contact their physician if no improvement occurs 3.
For patients with CURB-65 scores ≥3, promptly evaluate for potential ICU admission using IDSA/ATS severe CAP criteria rather than CURB-65 alone. 1, 5