CURB-65 Score Calculator for Community-Acquired Pneumonia

CURB-65 is a short prognostic score for assessing the severity of community-acquired pneumonia (CAP), developed by W. S. Lim et al. (Thorax, 2003) based on a multicenter study of three patient cohorts in the United Kingdom, New Zealand, and the Netherlands. The acronym stands for Confusion, Urea (blood urea), Respiratory rate, Blood pressure, and age 65 years or older — each feature present scores 1 point.

The score addresses the central question at presentation: where to treat a patient with pneumonia — as an outpatient, on a general ward, or in the intensive care unit. According to the original study, 30-day mortality is approximately 1.5% at a score of 0–1, 9% at a score of 2, and 22% at a score of 3 or higher. Major society guidelines for community-acquired pneumonia, including IDSA/ATS, recommend CURB-65 alongside PSI as a standard severity-stratification tool.

The main advantage of CURB-65 is its simplicity: 5 parameters, none of which require anything beyond routine biochemistry. This makes it convenient for use in the emergency department and outpatient settings. The simplified CRB-65 variant (without the urea criterion) is used in the prehospital setting and where laboratory testing is not readily available.

• Initial triage of an adult patient with confirmed or probable community-acquired pneumonia in the emergency department.
• Deciding the site of care: outpatient, general medical ward, or ICU.
• Documenting severity in the medical record and justifying hospitalization for insurance purposes.
• Teaching residents and students clinical reasoning in the management of pneumonia (a standard of clinical propaedeutics).
• Reassessment at 24-48 hours to detect deterioration and escalate care.

Confusion

Acute confusion: disorientation in time, place, or person, or an Abbreviated Mental Test Score (AMTS) ≤ 8. Chronic cognitive impairment in older adults is not counted on its own — what matters is an acute change.

Urea > 7 mmol/L

Serum urea > 7 mmol/L (equivalent to BUN > 19 mg/dL in English-language sources). Reflects dehydration and renal impairment in the setting of infection.

Respiratory rate ≥ 30/min

Respiratory rate ≥ 30/min — an independent predictor of severity in patients with pneumonia. Must be counted over a full minute, not extrapolated from 15 seconds.

BP: SBP < 90 or DBP ≤ 60 mm Hg

Systolic BP < 90 mm Hg OR diastolic BP ≤ 60 mm Hg. Either criterion alone is sufficient. Baseline hypotension in the patient is not a reason to disregard this criterion.

Age ≥ 65 years

Age ≥ 65 years at the time of assessment. The age criterion accounts for immunosenescence, multimorbidity, and reduced functional reserve.

• Not validated for immunocompromised patients (HIV, chemotherapy, glucocorticoids).
• Not intended for hospital-acquired (nosocomial) pneumonia — other scores are used instead (e.g., IDSA/ATS criteria).
• In young patients with severe pneumonia, the score may underestimate severity because age contributes little — clinical judgment takes priority over the score.
• Does not replace assessment of oxygenation: SpO2 and pO2 are not directly included; significant respiratory failure can occur despite a low score.
• Should be used with caution in pregnant patients: physiologic tachypnea and hypotension may distort the result.