CURB-65 Score Calculation Criteria
The CURB-65 score is calculated by assigning 1 point for each of the following five criteria: Confusion, Urea >7 mmol/L, Respiratory rate ≥30/min, low Blood pressure (SBP <90 mmHg or DBP ≤60 mmHg), and Age ≥65 years. 1, 2
Detailed Criteria Breakdown
Confusion
- New-onset mental confusion or disorientation
- Altered mental status
- This criterion has the strongest association with mortality (odds ratio 22.148) 3
Urea >7 mmol/L (BUN >19 mg/dL)
- Blood urea nitrogen level above threshold
- Strongly associated with sequential organ failure assessment scores 3
Respiratory rate ≥30 breaths per minute
- Measured at rest
- Indicates respiratory distress
Blood pressure
- Systolic BP <90 mmHg OR
- Diastolic BP ≤60 mmHg
- Note: Some studies suggest this may be less predictive of mortality in certain settings 3
Age ≥65 years
- Strong association with costs and resource utilization 3
Score Interpretation and Risk Stratification
| CURB-65 Score | Mortality Risk | Recommended Management |
|---|---|---|
| 0-1 | 0.7-2.1% | Outpatient treatment |
| 2 | 9.2% | Short hospital stay or supervised outpatient treatment |
| 3-5 | 14.5-57% | Hospital admission, assess for ICU |
Clinical Application
The CURB-65 score helps determine:
- Appropriate treatment setting (outpatient vs. inpatient)
- Need for ICU admission
- Intensity of monitoring required
- Breadth of antibiotic coverage
Important Considerations
- The CURB-65 score should be used alongside clinical judgment, not as a replacement 2
- Patients with bilateral lung infiltrates consistent with primary viral pneumonia should be managed as having severe pneumonia regardless of CURB-65 score 2
- The score may underestimate severity in young patients without comorbidities who develop severe respiratory failure 1
- A simplified version called CRB-65 (omitting urea measurement) can be used in outpatient settings where laboratory testing is unavailable 1, 4
Limitations
- Does not account for comorbidities or oxygenation status
- May not identify all patients requiring ICU admission
- Performance varies across different patient populations
- In nursing home-acquired pneumonia, even CRB-80 fails to identify truly low-risk patients 5
The CURB-65 score provides a standardized approach to risk stratification in community-acquired pneumonia, helping clinicians make evidence-based decisions about appropriate level of care and treatment intensity.