The CURB-65 score helps clinicians decide whether a patient with community-acquired pneumonia can be managed at home or needs hospital — and how aggressively. It uses five quick, objective criteria, each worth one point.
How it works
One point is added for each criterion that is present, for a total from 0 to 5:
- C — new mental Confusion.
- U — blood Urea greater than 7 mmol/L (roughly 19 mg/dL of BUN).
- R — Respiratory rate of 30 breaths per minute or more.
- B — low Blood pressure: systolic below 90 mmHg or diastolic of 60 mmHg or below.
- 65 — age 65 years or over.
The total maps to a recommended management band and an approximate 30-day mortality:
- 0–1 — low risk (~1.5%): consider home treatment.
- 2 — intermediate risk (~9%): short inpatient stay or closely supervised outpatient care.
- 3–5 — high risk (~22%): admit; assess for intensive care, especially at 4–5.
Applying each criterion correctly
Confusion (C) refers to new acute confusion, not pre-existing cognitive impairment. A patient with established dementia who is at their baseline does not score a point for C. A previously lucid patient who is disoriented to time and place on arrival does. The standard test is orientation to time, place and person.
Urea (U) uses the UK/international standard of 7 mmol/L. To convert to BUN in mg/dL (US convention): multiply by 2.8, so 7 mmol/L ≈ 19.6 mg/dL. If only creatinine is available, urea cannot be directly substituted — use CRB-65 instead.
Respiratory rate (R) is measured at rest for a full minute. A rate of 30 or more is the threshold. This criterion is particularly sensitive to measurement quality; a rushed 15-second count ×4 is less accurate, especially in a distressed patient.
Blood pressure (B) uses a disjunctive threshold: systolic below 90 or diastolic of 60 or below. Either alone scores the point.
Age 65 (65) — the patient must be 65 or older on the date of assessment.
Worked examples
Example 1 — low risk (score 0): A 55-year-old (no point) presents with cough and fever. Alert (no C), urea 5 mmol/L (no U), RR 18 (no R), BP 130/80 (no B). Score: 0. Management: consider home antibiotics with safety-netting.
Example 2 — high risk (score 3): A 72-year-old (1 point for age) with confusion (1) and RR 34 (1), urea 6.5 (no U), BP 110/70 (no B). Score: 3. Management: admit to hospital, assess for ICU suitability.
Example 3 — borderline (score 2): A 68-year-old (1) with urea 9 mmol/L (1), alert, RR 22, BP 135/85. Score: 2. Management: short inpatient stay or close outpatient follow-up, guided by oxygen saturation and comorbidities.
CURB-65 versus CRB-65
When a blood result is unavailable — in a GP surgery, community setting, or resource-limited environment — the CRB-65 score drops the U criterion and scores 0–4 instead of 0–5:
| CRB-65 score | Interpretation |
|---|---|
| 0 | Low risk — likely suitable for home treatment |
| 1–2 | Intermediate — hospital assessment recommended |
| 3–4 | High risk — urgent hospital admission |
CRB-65 is slightly less discriminating than CURB-65 at the middle of the range because the urea criterion adds prognostic information beyond age alone. Where blood results are available, CURB-65 is preferred.
Limitations and clinical judgement
The score guides, it does not decide. Several factors can override a low score:
- Hypoxia — SpO₂ below 94% (or below 90% in known COPD) indicates significant physiological compromise regardless of the CURB-65 score.
- Comorbidities — immunosuppression, active malignancy, and severe COPD all worsen prognosis beyond what the five criteria capture.
- Social circumstances — a score of 1 in a patient who lives alone, cannot take oral medication reliably, or has no one to monitor deterioration may still warrant admission.
- Unusual organisms — suspected atypical pneumonia, Legionella, or aspiration pneumonia may need inpatient assessment and IV therapy regardless of score.
CURB-65 is a decision aid validated for community-acquired pneumonia. It is not validated for hospital-acquired pneumonia, aspiration pneumonia, or pneumonia in immunocompromised patients.
Example and notes
A 70-year-old (1) with a respiratory rate of 32 (1) and a systolic of 85 mmHg
(1), but no confusion and a normal urea, scores 3 — high risk, admit.
CURB-65 is a decision aid, not a substitute for judgement. Hypoxia, comorbidity, and social factors can shift the decision either way. Where a urea result is not available, the related CRB-65 (0–4) can be used at the bedside.