CURB-65 Score (Pneumonia Severity)

The CURB-65 Score calculates pneumonia severity to guide disposition decisions: outpatient treatment, hospital admission, or ICU care. Developed by the British Thoracic Society, CURB-65 uses five readily available clinical criteria to stratify community-acquired pneumonia (CAP) patients by 30-day mortality risk. It is one of the most widely validated and used pneumonia severity scores globally.

The five criteria (each worth 1 point): Confusion (new onset mental confusion, AMT score of 8 or less), Urea (BUN greater than 19 mg/dL or blood urea greater than 7 mmol/L), Respiratory rate (30 or more breaths per minute), Blood pressure (systolic below 90 or diastolic 60 or below), and age 65 or older. The score ranges from 0 to 5, with higher scores indicating greater severity.

Mortality by score: 0 points: 0.7%, 1 point: 3.2%, 2 points: 13%, 3 points: 17%, 4 points: 41.5%, 5 points: 57%. BTS guidelines recommend: score 0-1 = outpatient management, score 2 = consider hospital admission or closely supervised outpatient care, score 3-5 = hospital admission with ICU consideration for scores 4-5.

CRB-65 (without urea testing) can be used in primary care where blood work is not immediately available, using only clinical assessment criteria. CRB-65 performs similarly to CURB-65 for low-risk identification and is endorsed by NICE guidelines for initial community assessment. A CRB-65 of 0 supports outpatient management.

Compared to the Pneumonia Severity Index (PSI/PORT), CURB-65 is simpler (5 variables vs 20), more practical in emergency settings, and equally effective at identifying low-risk patients suitable for outpatient care. However, PSI may be superior for identifying very low-risk patients and incorporates more clinical nuance. Neither score replaces clinical judgment; they are decision-support tools.

Important considerations: CURB-65 may underestimate severity in young patients with severe pneumonia (who score low on age and possibly urea), and may overestimate severity in elderly patients who score high on age alone. Additional factors including hypoxemia, multilobar infiltrates, comorbidities, and social circumstances should influence disposition decisions beyond the numerical score.