CURB-65 Calculator

CURB-65 Score Interpretation

💡 CRB-65 variant: If BUN is unavailable (e.g., primary care), use CRB-65 (omit Urea). Score ≥2 suggests hospitalization needed. No lab required — fully bedside.

Score	Risk Class	30-Day Mortality	Recommended Disposition
0	Low	0.6%	Outpatient treatment
1	Low	1.5%	Outpatient treatment
2	Moderate	9.2%	Consider short inpatient or supervised outpatient
3	High	22%	Hospitalize; consider HDU/ICU monitoring
4	High	33%	Hospitalize; consider ICU admission
5	High	57%	ICU admission strongly considered

About CURB-65

The CURB-65 score (Lim WS, et al., Thorax 2003;58:377–382) was derived and validated in over 1,000 hospitalized pneumonia patients as a simple bedside tool to stratify community-acquired pneumonia (CAP) severity. It identifies patients requiring inpatient vs. outpatient treatment and correlates with 30-day all-cause mortality.

Criteria Explained

C — Confusion: New onset disorientation, agitation, or somnolence not explained by baseline dementia. Abbreviated Mental Test (AMT) score ≤8 out of 10. Identifies altered mental status, a strong predictor of mortality in pneumonia.
U — Urea (BUN) > 19 mg/dL: Reflects prerenal azotemia from dehydration and systemic inflammation. BUN >7 mmol/L in SI units. Requires a lab result — the only criterion needing laboratory data. Elevated BUN independently predicts mortality and need for hospitalization.
R — Respiratory Rate ≥ 30/min: Tachypnea indicates respiratory compensation and severe infection. A classic marker of systemic inflammatory response in pneumonia.
B — Blood Pressure <90/60 mmHg: Hypotension indicates hemodynamic compromise and sepsis risk. Both systolic <90 mmHg and diastolic ≤60 mmHg each independently score the point — either qualifies.
65 — Age ≥ 65: Age ≥65 years old. Older age independently increases pneumonia mortality, reflecting declining physiologic reserve and higher comorbidity burden.

CURB-65 vs. CRB-65 vs. PSI/PORT

The CURB-65 and its simplified variant CRB-65 (drop the Urea/BUN criterion) are identical in scoring methodology — CRB-65 simply removes the laboratory requirement. CRB-65 is scored at the bedside with no blood work, making it ideal for prehospital, primary care, or ED triage before labs return. A CRB-65 ≥2 suggests the need for hospitalization.

The PSI/PORT score is a more comprehensive pneumonia severity score used primarily for discharge vs. admission decisions in the ED. PSI/PORT uses 20 variables including lab values, vital signs, and comorbidities, and is more accurate but much more complex to calculate. Use PSI/PORT when CURB-65 gives borderline results or when additional risk granularity is needed.

When CURB-65 Does NOT Apply

Do not use CURB-65 for:

Hospital-acquired pneumonia (HAP) or ventilator-associated pneumonia (VAP) — use clinical criteria or ICU scoring systems (APACHE II, SAPS II)
Immunocompromised patients — HIV/AIDS, chemotherapy, transplant — mortality risk is higher and CURB-65 underestimates severity
Aspiration pneumonia — often requires different management and has different mortality predictors
Known or suspected lung cancer — malignancy changes prognosis entirely
Pediatric pneumonia — use Pediatric Respiratory Severity Score (PRISM) or other pediatric-specific tools
COVID-19 pneumonia — dedicated COVID severity tools (NEWS2, SOFA) are more appropriate

Clinical Integration

CURB-65 should be used alongside clinical judgment and comorbidities. A score of 0–1 in a young, otherwise healthy patient is reassuring for outpatient management. However, a score of 2 in an elderly patient with heart failure, COPD, or immunosuppression warrants admission even if outpatient management might be considered in a younger, healthier patient. Conversely, a score of 2 in a healthy 40-year-old with pneumonia may still be appropriate for outpatient treatment with close follow-up.

Always consider social factors — ability to take oral medications, reliable follow-up, home support — when deciding disposition for low-risk scores. A score of 0–1 does not automatically mean outpatient is safe if social circumstances are unfavorable.

References

Lim WS, van der Eerden MM, Laing R, et al. Defining community acquired pneumonia severity on presentation to hospital: an objective derivation. Thorax. 2003;58(5):377–382. doi: 10.1136/thorax.58.5.377

National Institute for Health and Care Excellence (NICE). Pneumonia in adults: diagnosis and management. NICE guideline [NG191]. Published December 2021.

Criteria — Check Each That Applies