Calculator Guides
CURB-65 Score: Complete Clinical Guide
CURB-65 is a 5-point bedside severity score for community-acquired pneumonia: Confusion, Urea >7 mmol/L, Respiratory rate ≥30, Blood pressure (systolic <90 or diastolic ≤60), and age ≥65. Score 0–1 = low mortality (<3%), suitable for outpatient treatment.
TL;DR: CURB-65 is a 5-point bedside severity score for community-acquired pneumonia: Confusion, Urea >7 mmol/L, Respiratory rate ≥30, Blood pressure (systolic <90 or diastolic ≤60), and age ≥65. Score 0–1 = low mortality (<3%), suitable for outpatient treatment. Score ≥3 = severe, warrants ICU consideration. CURB-65 is simpler than PSI but misses some high-risk patients — know when each tool is appropriate.
What Is the CURB-65 Score?
CURB-65 was developed by W. Lim and colleagues and published in Thorax in 2003 as a simplified version of the earlier British Thoracic Society (BTS) pneumonia severity score. Its design priority was bedside speed.
It's endorsed by the British Thoracic Society, IDSA/ATS (as an adjunct to PSI), and is one of the most used pneumonia severity scores worldwide.
How to Calculate CURB-65
One point for each:
| Criterion | Definition | Points |
|---|---|---|
| C — Confusion | New disorientation (AMTS ≤8) | 1 |
| U — Urea | BUN >19 mg/dL (urea >7 mmol/L) | 1 |
| R — Respiratory rate | ≥30 breaths per minute | 1 |
| B — Blood pressure | Systolic <90 OR diastolic ≤60 mmHg | 1 |
| 65 — Age | ≥65 years | 1 |
Total: 0–5 points
CRB-65 (no lab version): Same but excludes urea. Useful when labs aren't immediately available.
Score Interpretation
| CURB-65 | 30-Day Mortality | Risk | Disposition |
|---|---|---|---|
| 0 | ~0.7% | Low | Outpatient |
| 1 | ~2.1% | Low | Outpatient with close follow-up |
| 2 | ~9.2% | Intermediate | Inpatient admission |
| 3 | ~14.5% | Severe | Inpatient; consider ICU |
| 4 | ~40% | Severe | ICU admission |
| 5 | ~57% | Severe | ICU admission |
Practical rule of thumb:
- Score 0–1: Treat as outpatient
- Score 2: Admit; floor or observation
- Score 3–5: Admit; ICU consideration for ≥3
Clinical Applications
Emergency Department Triage
CURB-65 is most useful at the point of care in the ED. A 72-year-old with pneumonia who is confused (C+1), BUN 24 (U+1), and age ≥65 (+1): CURB-65 = 3. Admit, consider ICU-level monitoring.
Antibiotic Stewardship
Low-risk patients (score 0–1) are candidates for oral monotherapy. High-risk patients (score ≥3) warrant dual therapy.
Case Vignettes
Case 1: 58-year-old with fever, productive cough, consolidation on X-ray. Alert, BUN 14, RR 22, BP 118/76, age 58. CURB-65 = 0. Discharge with oral amoxicillin-clavulanate.
Case 2: 78-year-old nursing home resident. Confused (C+1), BUN 32 (U+1), RR 34 (R+1), BP 88/55 (B+1), age 78 (65+1). CURB-65 = 5. ICU admission. IV beta-lactam + macrolide.
Case 3: 65-year-old with unilateral pneumonia. Alert, BUN 21 (U+1), RR 28, BP 110/70, age 65 (65+1). CURB-65 = 2. Admit to medical floor.
Limitations and Considerations
CURB-65 underestimates risk in some populations. Young patients (<65) with significant comorbidities can have serious pneumonia despite low scores.
CURB-65 performs worse than PSI for identifying low-risk patients. PSI stratifies more granularly but requires 20 variables.
Social factors aren't captured. A patient with CURB-65 of 1 who lives alone with poor health literacy should be admitted.
COVID-19 pneumonia: CURB-65 performed variably. SpO₂ and inflammatory markers were more predictive in COVID-19.
Evidence and Guidelines
Sligl WI and Marrie TJ (2013) confirmed that CURB-65 provides rapid bedside severity stratification with 30-day mortality estimates consistent across validation cohorts. Crit Care Clin. 2013;29(3):563–601. PMID: 23830654. DOI: 10.1016/j.ccc.2013.03.009
Carlos P et al. (2023) studied CURB-65 and long-term outcomes. High-risk groups (score >2) showed 13% inpatient mortality rising to 21.5% at 6 months. Cureus. 2023;15(3):e36052. PMID: 37056522. DOI: 10.7759/cureus.36052
Cilloniz C et al. (2023) compared CURB-65 against ML models and PSI. PSI matched ML performance (AUC 0.830); CURB-65 had slightly lower discrimination (AUC 0.764) but remains clinically practical. Chest. 2022;163(1):77–88. PMID: 35850287. DOI: 10.1016/j.chest.2022.07.005
IDSA/ATS 2007 guidelines recommend using either CURB-65 or PSI for disposition decisions in CAP.
Frequently Asked Questions
Q: When should I use PSI instead of CURB-65? When you have time and resources. PSI is more accurate for identifying low-risk patients safe for outpatient treatment.
Q: Does CURB-65 guide antibiotic duration? No — it determines severity and site of care, not duration.
Q: How does procalcitonin add to CURB-65? Procalcitonin helps distinguish bacterial from viral pneumonia and can guide antibiotic initiation. It complements severity scoring.
Related Calculators
- PSI/PORT Score — more granular pneumonia severity
- qSOFA — sepsis risk in pneumonia patients
- SOFA Score — organ dysfunction severity
- APACHE II — ICU-level severity scoring
References
- Sligl WI, Marrie TJ. Severe community-acquired pneumonia. Crit Care Clin. 2013;29(3):563–601. PMID: 23830654. DOI: 10.1016/j.ccc.2013.03.009
- Carlos P, Gomes R, Coelho J, et al. CURB-65 and Long-Term Mortality of Community-Acquired Pneumonia. Cureus. 2023;15(3):e36052. PMID: 37056522. DOI: 10.7759/cureus.36052
- Cilloniz C, Ward L, Mogensen ML, et al. Machine-Learning Model for Mortality Prediction in Patients With Community-Acquired Pneumonia. Chest. 2022;163(1):77–88. PMID: 35850287. DOI: 10.1016/j.chest.2022.07.005
- Lim WS, van der Eerden MM, Laing R, et al. Defining community acquired pneumonia severity on presentation to hospital. Thorax. 2003;58(5):377–382. PMID: 12728155.
- Mandell LA, Wunderink RG, Anzueto A, et al. IDSA/ATS consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. 2007;44 Suppl 2:S27–72. PMID: 17278083.