CURB-65 is a validated clinical scoring tool for assessing the severity of community-acquired pneumonia. Each letter stands for one criterion — Confusion, Urea, Respiratory rate, Blood pressure, and age 65 or over — and each present criterion adds one point to a score from 0 to 5.
Confusion: new disorientation to person, place, or time (an abbreviated mental test score of 8 or less is the formal threshold). Urea: blood urea nitrogen above 7 mmol/L (19 mg/dL) — this is the one criterion that needs a blood test, so a simplified CRB-65 version (dropping urea) exists for settings without immediate lab access. Respiratory rate: 30 breaths per minute or more. Blood pressure: systolic below 90 mmHg or diastolic 60 mmHg or below. Age: 65 or over.
A score of 0–1 indicates low severity, with a low risk of death — typically suitable for treatment at home. A score of 2 indicates moderate severity, and hospital referral or a hospital-supervised outpatient pathway is usually considered. A score of 3–5 indicates high severity and a higher risk of death — hospital admission is recommended, with assessment for intensive or high-dependency care especially at the top of the range. This mirrors the pathway set out in NICE guideline NG138 (Pneumonia in adults) and the original British Thoracic Society validation study.
CURB-65 is a severity-of-illness score, not a substitute for clinical judgement — treatment decisions remain with the treating clinician and should always account for the full clinical picture, including comorbidities, oxygen saturation, and social circumstances that the score itself doesn't capture. It was validated in adults with confirmed community-acquired pneumonia and is not intended for other respiratory presentations.
Criteria and severity bands: Lim et al., Thorax 2003 (the original CURB-65 validation study), as adopted by NICE NG138 — Pneumonia in adults: diagnosis and management.