Quick answer: Score 1 point each for Confusion (new onset), Urea >7 mmol/L (BUN >20 mg/dL), Respiratory rate ≥30/min, Blood pressure (systolic <90 or diastolic ≤60 mmHg), and Age ≥65 years. Total 0–5. Score 0–1: outpatient. Score 2: consider hospital admission. Score 3–5: urgent inpatient care — 30-day mortality exceeds 15–40%. Use our free CURB-65 calculator for instant scoring and documentation.
What Is the CURB-65 Score?
The CURB-65 is a validated clinical severity scoring system for community-acquired pneumonia (CAP), developed by Lim et al. and endorsed by the British Thoracic Society (BTS) in 2003. It uses five bedside criteria to estimate 30-day mortality risk and guide site-of-care decisions — specifically whether a patient with pneumonia should be treated as an outpatient, admitted to a general ward, or escalated to ICU-level care.
CURB-65 was designed to be simpler than the Pneumonia Severity Index (PSI), which requires 20 variables including laboratory values and chest X-ray findings. CURB-65 uses only five criteria, all obtainable at the bedside within minutes of patient contact.
Who Developed CURB-65 and When
Lim WS, van der Eerden MM, Laing R, et al. published the validation study in Thorax in 2003 (PMID: 12728155), confirming the score’s predictive accuracy across three prospective cohorts of CAP patients in the UK, New Zealand, and the Netherlands. The BTS endorsed CURB-65 in the same year as the preferred severity scoring tool for CAP in adults.
The Five CURB-65 Criteria — Complete Scoring Guide
Each criterion scores 1 point if present, 0 if absent. Total possible score: 0–5.
| Letter | Criterion | Threshold / Definition | How to assess |
|---|---|---|---|
| C | Confusion | New onset confusion or disorientation | Test orientation: ask name, date, and location. Use Abbreviated Mental Test Score (AMTS) ≤8 as the formal threshold. New confusion only — do not score if chronic cognitive impairment is baseline. |
| U | Urea (Blood Urea Nitrogen) | Urea >7 mmol/L (BUN >20 mg/dL) | Blood test. In patients without BUN result, use clinical markers of dehydration or renal impairment as a proxy — but document that BUN was not available. The CRB-65 (no U) is preferred in primary care when bloods aren’t immediately available. |
| R | Respiratory rate | RR ≥30 breaths per minute | Count respiratory rate over a full 60 seconds. Do not estimate. Tachypnoea is one of the most sensitive clinical markers of respiratory compromise in pneumonia. |
| B | Blood pressure | Systolic <90 mmHg OR diastolic ≤60 mmHg | One abnormal BP criterion = 1 point. Either systolic OR diastolic meeting threshold is sufficient — do not require both. |
| 65 | Age ≥65 years | Patient is 65 years old or older | Confirmed from patient record. This criterion reflects the exponentially increased mortality risk of pneumonia in older adults regardless of other presenting features. |
Memory aid: CURB-65 — Confused, Uraemic, Rapid breathing, Blood pressure low, 65 or older.
CURB-65 Score Interpretation — Mortality and Admission Decisions
| CURB-65 Score | Risk Group | 30-day Mortality | Recommended Action |
|---|---|---|---|
| 0 | Low | ~0.7% | Outpatient treatment appropriate in most cases. Ensure adequate follow-up within 24–48 hours. |
| 1 | Low | ~2.1% | Outpatient treatment usually appropriate. Consider short hospital stay if social factors or clinical concerns exist. |
| 2 | Intermediate | ~9.2% | Consider hospital admission and supervised management. Clinical judgement required — some CURB-65 score 2 patients may be suitable for outpatient care with close monitoring. |
| 3 | High | ~14.5% | Urgent hospital admission required. Assess need for ICU review. Begin empirical antibiotics immediately. |
| 4 | High | ~27.0% | Urgent hospital admission. Strong consideration for ICU or HDU level care. Senior review essential. |
| 5 | Severe | ~27–40%+ | Severe CAP. ICU admission should be considered. Aggressive resuscitation, broad-spectrum antibiotics, and monitoring. |
Critical clinical caveat: CURB-65 is a decision-support tool, not a replacement for clinical judgement. A patient with CURB-65 score 1 who has rapidly deteriorating oxygenation, bilateral consolidation on chest X-ray, or significant comorbidities may require hospital admission regardless of the low score. Always integrate the score with the full clinical picture.
CRB-65 — The Primary Care Version (No Blood Test Required)
When blood urea nitrogen is not immediately available (community setting, GP surgery, nursing home), the CRB-65 score can be used. It omits the Urea criterion and scores only four parameters: Confusion, Respiratory rate ≥30, Blood pressure low, Age ≥65. Maximum score: 4.
| CRB-65 Score | 30-day Mortality | Recommendation |
|---|---|---|
| 0 | ~1.2% | Low risk — home treatment likely appropriate |
| 1–2 | ~8.2% | Intermediate risk — hospital assessment recommended |
| 3–4 | ~31% | High risk — urgent hospital admission |
CURB-65 vs PSI — Which Should You Use?
| Feature | CURB-65 | PSI (PORT Score) |
|---|---|---|
| Number of variables | 5 | 20 |
| Blood tests required | Urea only | 7 laboratory values |
| Chest X-ray required | No | Yes |
| Time to calculate | 2 minutes bedside | 10–15 minutes with labs |
| Sensitivity for high-risk patients | 96.7% (for ICU admission) | Slightly lower |
| Specificity for low-risk patients | Lower — may over-admit younger patients | Better — more granular risk stratification |
| Best setting | Emergency department, acute medicine, ICU triage | Inpatient care planning, research |
| Endorsed by | BTS, NICE, IDSA/ATS (alongside PSI) | IDSA/ATS (alongside CURB-65) |
Bottom line: CURB-65 is better for rapid bedside triage and ICU admission prediction. PSI is better for identifying truly low-risk patients who can safely avoid hospitalisation. Both IDSA and ATS recommend using either CURB-65 or PSI — not one exclusively.
CURB-65 and COVID-19 Pneumonia — Important Limitations
CURB-65 was validated in bacterial community-acquired pneumonia. Its performance in COVID-19 pneumonia is significantly reduced for three reasons:
- Silent hypoxaemia: COVID-19 patients frequently present with severe hypoxaemia (SpO₂ <90%) without tachypnoea — the “happy hypoxic” phenomenon. CURB-65 does not include oxygen saturation, so these patients score falsely low.
- Age bias: The age ≥65 criterion over-weights age in COVID-19 where younger adults can develop severe disease, while older adults with mild COVID may be over-admitted.
- Different pathophysiology: COVID-19 pneumonia involves cytokine storm and endothelial injury rather than the bacterial consolidation CURB-65 was designed for.
For COVID-19 pneumonia, WHO and NICE recommend using SpO₂ and the WHO severity classification rather than CURB-65 alone.
Worked Clinical Examples
Example 1 — Low Risk
55-year-old man with productive cough, fever, and right lower lobe consolidation on CXR. Alert and oriented. BUN 14 mg/dL. RR 18/min. BP 128/82 mmHg.
- C: No confusion = 0
- U: BUN 14 < 20 mg/dL = 0
- R: RR 18 < 30 = 0
- B: BP normal = 0
- 65: Age 55 < 65 = 0
- CURB-65 = 0 → Low risk (~0.7% mortality) → Outpatient treatment appropriate
Example 2 — High Risk
78-year-old woman with productive cough and 3-day fever. Confused, not oriented to date. BUN 28 mg/dL. RR 34/min. BP 86/58 mmHg.
- C: Confused = 1
- U: BUN 28 > 20 mg/dL = 1
- R: RR 34 ≥ 30 = 1
- B: BP systolic 86 < 90 = 1
- 65: Age 78 ≥ 65 = 1
- CURB-65 = 5 → Severe risk (~40% mortality) → Urgent ICU review required
SOAP Note Documentation Template
CURB-65 severity score calculated for community-acquired pneumonia. Criteria assessed: Confusion — new onset (1 point); Blood urea nitrogen 26 mg/dL, above 20 mg/dL threshold (1 point); Respiratory rate 32 breaths/min, ≥30 threshold (1 point); Blood pressure 118/76 mmHg, within normal range (0 points); Age 71 years, ≥65 threshold (1 point). Total CURB-65 score: 4/5 — High risk group. Estimated 30-day mortality: ~27%. Recommendation per BTS guidelines: urgent hospital admission with assessment for HDU/ICU-level care. Empirical antibiotics initiated. Senior review requested. Plan: serial CURB-65 and clinical reassessment at 12 hours.
Free CURB-65 Calculator
Our free CURB-65 calculator scores all five criteria, classifies risk group, displays 30-day mortality estimate, generates an admission recommendation, and produces EMR-ready documentation. No login required.
→ Open the free CURB-65 Calculator
Related ICU Calculators
- SOFA Score — organ dysfunction and sepsis identification
- PF Ratio (PaO₂/FiO₂) — respiratory failure severity in pneumonia
- APACHE II Score — ICU mortality prediction for admitted patients
Frequently Asked Questions
What does CURB-65 stand for?
CURB-65 stands for: Confusion (new onset), Urea >7 mmol/L (BUN >20 mg/dL), Respiratory rate ≥30/min, Blood pressure low (systolic <90 or diastolic ≤60 mmHg), and 65 = age ≥65 years. Each criterion scores 1 point for a maximum of 5.
What CURB-65 score requires ICU admission?
A CURB-65 score of 3 or above indicates high mortality risk and should prompt urgent hospital admission with assessment for ICU or HDU-level care. A score of 4–5 has 30-day mortality of 27–40% and warrants immediate senior review and ICU consideration.
Can CURB-65 be used in the community without blood tests?
Yes — use the CRB-65 variant, which omits the urea criterion. CRB-65 scores four parameters (Confusion, Respiratory rate, Blood pressure, Age ≥65) with a maximum of 4. CRB-65 score 0 = low risk, 1–2 = intermediate, 3–4 = high risk requiring urgent hospital admission.
Is CURB-65 validated for COVID-19?
No — CURB-65 has significantly reduced performance in COVID-19 pneumonia because it does not include oxygen saturation, and COVID-19 frequently causes silent hypoxaemia (severe hypoxia without tachypnoea). Use WHO severity classification and SpO₂ monitoring for COVID-19 severity assessment.
What is the difference between CURB-65 and PSI?
CURB-65 uses 5 variables and takes 2 minutes at the bedside — best for rapid ED triage and ICU admission prediction. The PSI (Pneumonia Severity Index) uses 20 variables including 7 lab values and chest X-ray — better for identifying truly low-risk patients safe for outpatient management. Both are endorsed by IDSA/ATS guidelines.
References
- Lim WS, van der Eerden MM, Laing R, et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax. 2003;58(5):377-382. PMID: 12728155.
- British Thoracic Society Standards of Care Committee. BTS guidelines for the management of community acquired pneumonia in adults. Thorax. 2001;56 Suppl 4:IV1-64. PMID: 11713364.
- 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.
- Zaki HA, Alkahlout BH, Shaban E, et al. The Battle of the Pneumonia Predictors: A Comprehensive Meta-Analysis Comparing PSI and CURB-65. Cureus. 2023;15(7):e42672. PMID: 37649987.
- Gelaidan A, Almaimani M, Alorfi YA, et al. Comparative Effectiveness of CURB-65 and qSOFA Scores in Predicting Pneumonia Outcomes. Cureus. 2024;16(10):e71394. PMID: 39525089.
Written by Nikhil Mahajan, PT, MPT | Last reviewed: June 2026 | Free CURB-65 Calculator →