What is the CURB-65 (Confusion, Urea, Respiratory rate, Blood pressure, and age 65 or older) scoring system?

CURB-65: Clinical Severity Score for Community-Acquired Pneumonia

CURB-65 is a validated 5-point clinical prediction tool that stratifies mortality risk in community-acquired pneumonia patients to guide hospital admission decisions, with each letter representing one clinical parameter that scores 1 point if present. 1, 2

The Five Components (Each Worth 1 Point)

• C = Confusion (new onset disorientation to person, place, or time) 1, 2
• U = Urea (Blood Urea Nitrogen >7 mmol/L or approximately >20 mg/dL) 1, 2
• R = Respiratory rate ≥30 breaths per minute 1, 2
• B = Blood pressure (systolic <90 mmHg OR diastolic ≤60 mmHg) 1, 2
• 65 = Age ≥65 years 1, 2

Risk Stratification and Management Recommendations

Score 0-1 (Low Risk):

• Mortality risk: 0.7-2.1% 2, 3
• Recommendation: Consider outpatient treatment 1, 2
• These patients can safely be managed at home with oral antibiotics 1

Score 2 (Intermediate Risk):

• Mortality risk: 9.2% 2, 3
• Recommendation: Consider short hospital stay or closely supervised outpatient treatment 1, 2
• Clinical judgment is particularly important in this group 2

Score 3 (High Risk):

• Mortality risk: 14.5% 2, 3
• Recommendation: Hospital admission with assessment for ICU 2

Score 4-5 (Very High Risk):

• Mortality risk: 40-60% 2, 3
• Recommendation: Hospital admission with urgent ICU assessment 2

Clinical Application Algorithm

Step 1: Calculate the score at point of care by assessing all five parameters 1

Step 2: Apply the risk stratification above, but recognize that CURB-65 must support, not replace, clinical judgment 1, 2

Step 3: Override the score when external factors are present 1, 2:

• Important comorbidities not captured by the score (HIV, immunosuppression) 1, 2
• Failure of prior outpatient antibiotic therapy 1, 2
• Social factors affecting medication adherence or follow-up 1, 2
• Need for procedures (pleural drainage, supplemental oxygen) 1

Advantages Over Other Scoring Systems

• Simplicity: Only 5 variables compared to 20 in the Pneumonia Severity Index (PSI), making it practical at the bedside 1, 2
• Minimal laboratory requirements: Only one blood test (urea/BUN) needed 2
• Speed: Can be calculated rapidly in emergency settings 2
• Validated effectiveness: Endorsed by American Thoracic Society, British Thoracic Society, and IDSA guidelines 1, 2

Simplified Alternative: CRB-65

When laboratory testing is unavailable, use CRB-65 (omits the Urea component, scoring 0-4 points instead of 0-5) 1, 2

• Particularly useful in outpatient clinics and resource-limited settings 2
• Maintains reasonable predictive accuracy without requiring blood work 1

Important Limitations and Pitfalls

CURB-65 may underestimate severity in: 2, 4

• Young patients (<65 years) with severe respiratory failure who lack age points
• Patients requiring critical care interventions despite low scores (15.6% of score 0-1 patients were admitted to ICU in one study) 4

CURB-65 performs less well for: 2

• ICU admission decisions specifically (use IDSA/ATS severe CAP criteria instead)
• Elderly nursing home patients with multiple comorbidities 5

Common pitfall: A score of 2 represents a "gray zone" where 27% required ICU admission and 15.4% needed critical care interventions 4. Do not automatically discharge these patients without careful assessment.

Practical Clinical Example

A 62-year-old patient with cough, fever, respiratory rate 24/min, normal blood pressure, no confusion, and BUN 14 mg/dL scores 0 points (age <65, all other parameters normal), suggesting safe outpatient treatment despite elevated white blood cell count, which is not part of the scoring system 1