Clinical Overview

CURB-65 is a pragmatic severity score for adults with community-acquired pneumonia. Its five equally weighted items—new confusion, raised urea, tachypnea, low blood pressure, and age 65 years or older—identify increasing short-term mortality risk. It is calculated after pneumonia has been clinically established; it is not intended to distinguish pneumonia from bronchitis, pulmonary edema, pulmonary embolism, or other causes of respiratory symptoms.

The result supports, but does not dictate, the site-of-care decision. A clinician should examine oxygen saturation and oxygen requirement, work of breathing, radiographic extent, sepsis features, organ dysfunction, ability to take oral medication, pregnancy, frailty, comorbid disease, and the safety of follow-up. Where serum urea is not immediately available, CRB-65 omits urea, but its interpretation differs and should follow the relevant guideline.

When to Use

• Adults with community-acquired pneumonia after clinical diagnosis
• Severity and mortality-risk communication
• One component of admission and escalation planning

Limitations & Safety

The original score was derived and validated in hospitalized adults. Age automatically adds one point, which may overstate severity in a physiologically well older adult, while younger patients with severe hypoxemia or major comorbidity may receive a deceptively low score. Immunocompromise, aspiration, tuberculosis, recent hospitalization, resistant organisms, and complications such as empyema need specific assessment beyond the score.

Confusion should be new and attributable to the acute illness rather than stable cognitive impairment. Urea must be interpreted in the stated units: more than 7 mmol/L is approximately BUN over 19 mg/dL. The blood-pressure point is awarded if systolic pressure is below 90 mmHg or diastolic pressure is 60 mmHg or lower. Do not double-count both. Reassess after initial treatment when physiology changes, but base major decisions on the whole trajectory.

• Not validated for children
• Does not replace oxygenation, comorbidity, social, or oral-intake assessment
• Hospital-acquired pneumonia and profound immunosuppression require condition-specific evaluation

Formula / Scoring Criteria

CURB-65 = Confusion + Urea > 7 mmol/L (BUN > 19 mg/dL) + Respiratory rate ≥ 30/min + low Blood pressure (SBP < 90 or DBP ≤ 60 mmHg) + age ≥ 65 years

Interpretation

• 0–1 — Low risk: Approximate 30-day mortality commonly reported around 1–2%. Consider outpatient care only if no other clinical or social reason for admission exists.
• 2 — Intermediate risk: Approximate mortality around 9% in original cohorts. Consider hospital-supervised treatment or short inpatient care.
• 3–5 — High risk: Mortality rises substantially; scores 4–5 are especially concerning. Hospitalize; assess urgently for critical-care escalation and severe CAP management.

Evidence & References

1. Lim WS, et al. Defining community acquired pneumonia severity on presentation. Thorax. 2003.
2. Metlay JP, et al. ATS/IDSA Community-Acquired Pneumonia Guideline. 2019.
3. NICE guideline NG250: Pneumonia diagnosis and management.

Clinical FAQs

Can CURB-65 decide discharge by itself?

No. Oxygenation, oral intake, comorbidities, complications, adherence, home support, and clinician judgment remain essential.

What if only BUN is reported?

The urea criterion corresponds approximately to BUN greater than 19 mg/dL. Confirm the laboratory analyte and unit before entering it.

Is CURB-65 used in children?

No. Pediatric pneumonia severity and disposition should follow age-specific assessment and guidelines.