What is the CURB-65 score?

CURB-65 is a clinical prediction rule developed by Lim et al. (2003) to assess the severity of community-acquired pneumonia (CAP) and guide hospital admission decisions. Each letter represents one criterion: C = Confusion (new), U = Urea >7 mmol/L (BUN >19 mg/dL), R = Respiratory rate ≥30/min, B = Blood pressure <90 systolic or ≤60 diastolic mmHg, 65 = Age ≥65 years. Each criterion scores 1 point for a maximum of 5.

What CURB-65 score requires hospital admission?

CURB-65 score 0-1 = low severity, outpatient treatment appropriate, 30-day mortality approximately 0.6-1.5%. Score 2 = moderate severity, consider short inpatient stay or supervised outpatient care, mortality approximately 6.8%. Score 3-5 = high severity, hospital admission required; score 4-5 indicates possible ICU admission, with 30-day mortality of 27.8% and 40%+ respectively.

How is confusion defined in CURB-65?

In the original CURB-65 study, confusion is defined as an Abbreviated Mental Test (AMT) score of 8 or less, or new disorientation in person, place, or time. It must be new-onset confusion — pre-existing dementia or chronic cognitive impairment does not qualify. Clinically, any acute alteration in mental status in the context of pneumonia should be scored as confusion.

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

CURB-65 uses 5 simple criteria scored at the bedside in under 2 minutes, making it practical for emergency settings. PSI (Pneumonia Severity Index) uses 20 variables including laboratory values and co-morbidities, is more accurate but more complex. CURB-65 tends to over-admit younger patients with few comorbidities; PSI may under-admit elderly patients. British Thoracic Society guidelines recommend CURB-65; IDSA/ATS guidelines recommend PSI.

What is the CURB-65 score?

CURB-65 is a clinical prediction rule developed by Lim et al. (2003) to assess the severity of community-acquired pneumonia (CAP) and guide hospital admission decisions. Each letter represents one criterion: C = Confusion (new), U = Urea >7 mmol/L (BUN >19 mg/dL), R = Respiratory rate ≥30/min, B = Blood pressure <90 systolic or ≤60 diastolic mmHg, 65 = Age ≥65 years. Each criterion scores 1 point for a maximum of 5.

What CURB-65 score requires hospital admission?

CURB-65 score 0-1 = low severity, outpatient treatment appropriate, 30-day mortality approximately 0.6-1.5%. Score 2 = moderate severity, consider short inpatient stay or supervised outpatient care, mortality approximately 6.8%. Score 3-5 = high severity, hospital admission required; score 4-5 indicates possible ICU admission, with 30-day mortality of 27.8% and 40%+ respectively.

How is confusion defined in CURB-65?

In the original CURB-65 study, confusion is defined as an Abbreviated Mental Test (AMT) score of 8 or less, or new disorientation in person, place, or time. It must be new-onset confusion — pre-existing dementia or chronic cognitive impairment does not qualify. Clinically, any acute alteration in mental status in the context of pneumonia should be scored as confusion.

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

CURB-65 uses 5 simple criteria scored at the bedside in under 2 minutes, making it practical for emergency settings. PSI (Pneumonia Severity Index) uses 20 variables including laboratory values and co-morbidities, is more accurate but more complex. CURB-65 tends to over-admit younger patients with few comorbidities; PSI may under-admit elderly patients. British Thoracic Society guidelines recommend CURB-65; IDSA/ATS guidelines recommend PSI.

🫁 Community-Acquired Pneumonia · BTS Guidelines · 30-Day Mortality

CURB-65 Score Calculator

Score 5 clinical criteria to triage community-acquired pneumonia severity and determine outpatient, inpatient, or ICU disposition with 30-day mortality risk estimates.

NM Clinically reviewed byDr. Nikhil Mahajan, PT, MPT · Jan 15, 2025

0 0.6% Outpatient treatment

1 1.5% Outpatient (consider short stay)

2 6.8% Inpatient / Observation

3 14.5% Hospital admission

4 27.8% Hospital admission — consider ICU

5 ~40%+ ICU admission likely required

Score 1 Point for Each Criterion Present

Confusion (New Onset) AMT score ≤8 or new disorientation in person, place, or time — must be acute, not pre-existing dementia

Urea / BUN Elevated Blood Urea Nitrogen (BUN) >19 mg/dL OR serum urea >7 mmol/L — reflects renal hypoperfusion from sepsis

Respiratory Rate ≥30/min Tachypnea ≥30 breaths per minute — marker of respiratory compromise and work of breathing

Blood Pressure Low Systolic BP <90 mmHg OR diastolic BP ≤60 mmHg — indicates hemodynamic compromise

Age ≥ 65 Years Patient aged 65 years or older — age-related reduced physiological reserve increases mortality risk

CURB-65 Score 0 / 5

Low Severity — Outpatient

CURB-65 — 30-Day Mortality & Disposition Reference

Score	Severity	30-Day Mortality	Recommended Disposition
0	Low Severity	0.6%	Outpatient treatment
1	Low Severity	1.5%	Outpatient (consider short stay)
2	Moderate Severity	6.8%	Inpatient / Observation
3	High Severity	14.5%	Hospital admission
4	High Severity	27.8%	Hospital admission — consider ICU
5	Critical Severity	~40%+	ICU admission likely required

Based on Lim WS et al. Thorax. 2003;58(5):377-82. Estimates from original derivation cohort; local validation recommended.

CURB-65 — Clinical Reference for Pneumonia Triage

The CURB-65 score is a validated clinical prediction rule developed by Lim et al. (2003) to stratify the severity of community-acquired pneumonia (CAP) and guide hospital admission decisions. It assigns one point for each of five criteria — Confusion, Urea >7 mmol/L, Respiratory rate ≥30/min, Blood pressure <90/60 mmHg, and Age ≥65 years — for a maximum score of 5.

The 5 CURB-65 Criteria Explained

C — Confusion (New Onset): AMT score ≤8 or new disorientation in person, place, or time — must be acute, not pre-existing dementia
U — Urea / BUN Elevated: Blood Urea Nitrogen (BUN) >19 mg/dL OR serum urea >7 mmol/L — reflects renal hypoperfusion from sepsis
R — Respiratory Rate ≥30/min: Tachypnea ≥30 breaths per minute — marker of respiratory compromise and work of breathing
B — Blood Pressure Low: Systolic BP <90 mmHg OR diastolic BP ≤60 mmHg — indicates hemodynamic compromise
65 — Age ≥ 65 Years: Patient aged 65 years or older — age-related reduced physiological reserve increases mortality risk

CURB-65 Disposition Guidelines

Score 0–1 (Low severity, mortality 0.6–1.5%): Outpatient antibiotic therapy is appropriate for most patients. Consider short inpatient stay for score 1 patients with social concerns, inadequate home support, or inability to take oral medications.
Score 2 (Moderate severity, mortality 6.8%): Short inpatient stay or hospital-supervised outpatient care. Reassess frequently — patients can deteriorate rapidly. Consider IV antibiotics.
Score 3 (High severity, mortality 14.5%): Hospital admission required. Consider infectious disease or pulmonology consultation. Begin empiric broad-spectrum antibiotic therapy per BTS/IDSA guidelines.
Score 4–5 (Very high severity, mortality 27.8–40%+): Urgent hospital admission; assess need for ICU transfer. Consider vasopressors, mechanical ventilation support. ICU-level monitoring indicated.

CURB-65 vs PSI (Pneumonia Severity Index)

CURB-65 uses 5 simple bedside criteria requiring no laboratory values (except BUN) and can be completed in under 2 minutes — making it practical for busy emergency departments. PSI (PORT score) uses 20 variables including multiple laboratory values and comorbidities, is more discriminating but significantly more complex. British Thoracic Society guidelines recommend CURB-65; IDSA/ATS guidelines favour PSI. Both tools complement rather than replace clinical judgment.

Limitations of CURB-65

Does not account for oxygenation status (SpO₂ or PaO₂/FiO₂) — a patient with SpO₂ 85% on room air may score 0 and be categorized as low risk despite requiring oxygen therapy
May under-identify severity in younger patients with few comorbidities who deteriorate rapidly
May over-admit elderly nursing home residents with chronic cognitive impairment (confusion criterion)
Not validated for viral pneumonia (COVID-19, influenza) — use disease-specific tools for these populations

NM Dr. Nikhil Mahajan, PT, MPT · Reviewed January 15, 2025 · View credentials

Frequently Asked Questions

Can CURB-65 be used for COVID-19 pneumonia?

CURB-65 was developed and validated specifically for bacterial community-acquired pneumonia. While it provides a snapshot of respiratory distress severity, it has not been validated for viral pneumonia including COVID-19. Studies during the pandemic found CURB-65 underestimated severity in some COVID-19 patients who deteriorated despite low scores — particularly regarding oxygenation status, which CURB-65 does not capture. Use COVID-specific tools (NEWS2, ISARIC 4C Mortality Score) for COVID-19 triage alongside CURB-65.

What antibiotics are recommended for CURB-65 score 0-1?

For low-severity CAP (CURB-65 0–1) treated as outpatient: BTS guidelines recommend amoxicillin 500 mg three times daily for 5 days as first-line in patients without comorbidities. For patients with comorbidities (COPD, heart disease, immunosuppression) or where atypical organisms are suspected, doxycycline 200 mg loading dose then 100 mg daily, or a macrolide (clarithromycin, azithromycin) is recommended. This calculator provides triage guidance only — antibiotic selection should follow local antibiograms and formulary guidelines.

Should I use CRB-65 instead of CURB-65 in primary care?

CRB-65 omits the BUN criterion (which requires a blood test), using only Confusion, Respiratory rate, Blood pressure, and Age ≥65 — making it practical for primary care and community settings where blood tests are not immediately available. CRB-65 score 0 = low risk (outpatient); 1–2 = intermediate (consider admission); 3–4 = high risk (urgent hospital admission). CURB-65 is preferred in ED and hospital settings where BUN is routinely available and provides better discrimination between moderate and high severity.

What is the BUN threshold for CURB-65 in different units?

The CURB-65 BUN threshold is equivalent in both measurement systems: BUN >19 mg/dL (used in the United States) equals Serum Urea >7 mmol/L (used in the UK, Europe, Australia). Both represent the same degree of azotemia reflecting reduced renal perfusion from the pneumonia sepsis response. Use whichever unit your laboratory reports — they are directly convertible: BUN (mg/dL) × 0.357 = Urea (mmol/L).