How to Assign Pneumonia Risk Class Using CURB-65
Calculate the CURB-65 score by assigning 1 point for each of the following five criteria present: Confusion (mental test score <8 or new disorientation in person, place, or time), Urea >7 mmol/L, Respiratory rate ≥30/min, Blood pressure (systolic <90 mmHg or diastolic ≤60 mmHg), and Age ≥65 years—then stratify patients into risk classes 0-5 based on total points to guide site-of-care decisions. 1, 2
The CURB-65 Scoring System
The British Thoracic Society developed CURB-65 as a simple, bedside severity assessment tool that requires only basic clinical measures and one laboratory test (blood urea). 3 This makes it far more practical than the Pneumonia Severity Index (PSI), which requires extensive laboratory work, blood gases, and chest radiography data. 3
Calculate the Score (0-5 points total):
- C = Confusion: Mental test score <8, or new disorientation in person, place, or time (1 point) 1
- U = Urea: >7 mmol/L (1 point) 1
- R = Respiratory rate: ≥30 breaths/min (1 point) 1
- B = Blood pressure: Systolic <90 mmHg OR diastolic ≤60 mmHg (1 point) 1
- 65 = Age ≥65 years (1 point) 1
Risk Stratification and Management Decisions
Score 0-1: Low Risk (0.7-2.1% mortality)
- Outpatient treatment is appropriate 3
- These patients can safely receive home treatment with antibiotics 2
Score 2: Intermediate Risk (9.2% mortality)
- Consider short hospital stay or hospital-supervised outpatient treatment 3, 1
- This decision requires clinical judgment based on comorbidities, social circumstances, and ability to comply with outpatient therapy 1
Score 3-5: High Risk (14.5-57% mortality)
- Hospital admission mandatory 3, 1, 2
- Assess for ICU admission 3
- Scores of 4-5 specifically warrant consideration for HDU/ICU transfer 1, 2
Critical Caveats and Clinical Judgment
Do not rely on CURB-65 alone in these situations:
Bilateral lung infiltrates on chest radiography consistent with primary viral pneumonia should be managed as severe pneumonia regardless of CURB-65 score 1, 2
Young patients without comorbidities may have severe respiratory failure requiring ICU care despite low CURB-65 scores, as the tool can underestimate severity in this population 3
Elderly patients with comorbidities may be underestimated by CURB-65 alone 3
Hypoxemia (PaO2 <60 mmHg or O2 saturation <90% on room air) at presentation warrants hospital admission even with low CURB-65 scores 4
Additional Considerations for ICU Transfer
Beyond CURB-65 scores of 4-5, consider HDU/ICU transfer for: 1, 2
- Persisting hypoxia with PaO2 <8 kPa despite maximal oxygen
- Progressive hypercapnia
- Severe acidosis (pH <7.26)
- Septic shock
Simplified Alternative: CRB-65
If blood urea testing is unavailable (particularly in primary care or resource-limited settings), use CRB-65 which omits the urea measurement but maintains similar predictive value for identifying low-risk patients suitable for outpatient management. 3, 5
The CURB-65 remains the most practical and validated tool for pneumonia severity assessment in clinical practice, particularly effective at identifying low-risk patients who can avoid hospitalization while flagging high-risk patients requiring intensive monitoring. 3, 6, 3