Pulmonology

CURB-65 Pneumonia Severity Score

5 inputsPulmonology

Assess severity of community-acquired pneumonia (CAP).

Calculate

CURB-65 calculator

Result

0points

Low — home (~0.7% 30-day mortality)

How to use it

1
Assess confusion. AMT ≤8 or any new confusion qualifies.
2
Check urea. Blood urea > 7 mmol/L with admission bloods.
3
Count RR for 1 minute. ≥30 before supplemental O₂ if possible.

When to use it

Apply to all adults with confirmed or suspected community-acquired pneumonia to guide site-of-care decisions. Not validated for hospital-acquired pneumonia or in patients with structural lung disease.

CAP triage in ED/AMU: Guides outpatient vs. ward vs. HDU/ICU decision.
Antibiotic de-escalation: Improvement to CURB 0–1 supports oral step-down.
Not for HAP or immunocompromised: Different risk profiles require alternative scoring.

About the score

CURB-65 is the British Thoracic Society (BTS) validated severity scoring system for community-acquired pneumonia (CAP) in adults. It uses five variables to stratify patients into three risk groups, directly guiding site-of-care decisions: outpatient treatment, hospital admission, or HDU/ICU consideration. The five criteria — new confusion, raised urea, elevated respiratory rate, low blood pressure, and age ≥65 — each score one point, giving a maximum of 5. CURB-65 is simpler than the PSI/PORT score and is the preferred tool in UK clinical practice, endorsed by BTS and NICE.

Confusion, Urea, Respiratory rate, Blood pressure, Age ≥65

Scoring criteria

Confusion (new disorientation in person, place, or time): 1
Urea > 7 mmol/L (BUN > 20 mg/dL): 1
Respiratory rate ≥ 30 breaths/min: 1
Blood pressure: SBP < 90 or DBP ≤ 60 mmHg: 1
Age ≥ 65 years: 1

Score interpretation

0–1Low severityHome treatment appropriate in most cases (30-day mortality <3%)
2Moderate severityHospital-supervised treatment; consider short admission (mortality ~9%)
3–5High severityUrgent hospital admission; ICU/HDU assessment if score 4–5 (mortality 15–40%)

Guideline recommendation

BTS CAP Guidelines (2009): CURB-65 is the recommended scoring tool for severity assessment in CAP; NICE CG191 (2014) uses CRB-65 in primary care and CURB-65 in hospital. Score ≥3 requires hospital admission; score 4–5 warrants HDU/ICU consideration. Use alongside clinical judgement — social factors, comorbidities, and oxygen saturation also influence admission decisions.

Clinical pearls

CRB-65 (without urea) is a valid alternative in primary care where urea is not immediately available.
CURB-65 is a severity tool, not a diagnostic tool — clinical presentation (oxygen saturation, respiratory examination, radiological confirmation) must guide the diagnosis.
CURB-65 leaves out oxygenation: hypoxaemia warrants hospital assessment whatever the score. Oxygen targets differ: 94–98% for most adults, 88–92% in COPD with a risk of hypercapnic respiratory failure (BTS 2017 emergency oxygen guideline).
In older patients, confusion may be the presenting sign of sepsis rather than classical pneumonia symptoms.
A score of 2 is a clinical judgment zone — consider social circumstances, comorbidities, and trajectory before deciding on outpatient vs inpatient management.

Limitations

Less discriminating than PSI/PORT for identifying very low-risk patients suitable for outpatient treatment.
Urea requires blood testing, which may delay scoring in resource-limited settings.
Not validated for healthcare-associated pneumonia or immunocompromised patients.

A reference for clinicians and students, not medical advice. A score supports a decision; it does not make one. Check every result against the patient in front of you and your local protocol.

At a glance

Specialty: Pulmonology
Inputs: 5
Type: Points score
Guidelines from: BTS, NICE, IDSA

Frequently asked questions

What CURB-65 score requires hospital admission?

A CURB-65 score of ≥2 indicates moderate-to-high severity and requires at least hospital-supervised treatment. Scores of ≥3 mandate hospital admission. Scores of 4–5 require consideration of ICU or high-dependency unit admission due to 30-day mortality rates of 15–40%.

What is the difference between CURB-65 and PSI score for pneumonia?

CURB-65 is simpler, uses five variables, and is the BTS/NICE preferred tool in the UK. The Pneumonia Severity Index (PSI/PORT) uses 20 variables and is more accurate at identifying very-low-risk patients suitable for outpatient treatment. PSI is preferred in North American practice (IDSA/ATS guidelines).