CURB-65 Pneumonia Severity Score Calculator

About the CURB-65 Pneumonia Severity Score Calculator

The CURB-65 Pneumonia Severity Score Calculator is a validated severity worksheet for community-acquired pneumonia (CAP). Developed by Lim et al. (2003) from a study of more than 1,000 patients at 3 UK hospitals, CURB-65 uses five bedside variables to estimate 30-day mortality and provide care-setting context from the original cohorts.

The acronym CURB-65 stands for: Confusion (new-onset), Urea (BUN >19 mg/dL or >7 mmol/L), Respiratory rate (≥30/min), Blood pressure (SBP <90 or DBP ≤60), and age ≥65. Each criterion scores one point, yielding a total from 0 to 5. Lower scores generally track with lower short-term mortality, while higher scores are more often associated with inpatient or higher-acuity review.

This calculator auto-calculates criteria from entered vital signs and labs, provides both CURB-65 (with BUN) and CRB-65 (without lab work, for outpatient settings), and shows mortality data plus a criteria breakdown table. It is meant to support context, not replace bedside judgment.

When This Page Helps

Pneumonia severity is easy to underestimate when individual vital signs or labs are looked at in isolation. CURB-65 gives a compact way to summarize five major risk features and compare the resulting score with the original mortality data. That makes it useful as a worksheet for level-of-care conversations without turning the page into a stand-alone admit-or-discharge instruction.

How to Use the Inputs

1. Enter the patient's age.
2. Enter vital signs: respiratory rate, systolic and diastolic blood pressure.
3. Enter BUN (blood urea nitrogen) in mg/dL.
4. Indicate whether the patient has new mental confusion.
5. Review the auto-calculated CURB-65 score, mortality risk, and care-context summary.
6. Use CRB-65 (displayed alongside) when lab results are unavailable.

Example Calculation

Tips & Best Practices

• CURB-65 is usually calculated at presentation, and serial reassessment can help show whether the clinical picture is changing.
• CRB-65 (without urea) can be used in community settings when lab results are unavailable, but it is a simpler proxy and should be read more cautiously.
• CURB-65 is validated for community-acquired pneumonia; it should not be used for hospital-acquired, ventilator-associated, or aspiration pneumonia.
• Clinical judgment should always accompany CURB-65 — unstable comorbidities, empyema, multilobar disease, or inability to take oral medications can make the score look cleaner than the real bedside picture.
• The score does not account for oxygen requirement, imaging burden, lactate, or immunocompromise, so it should stay one input in a wider CAP assessment.
• The PSI (Pneumonia Severity Index) is an alternative scoring system with 20 variables; CURB-65 is simpler for early reference use.

CURB-65 Development and Validation

The original study by Lim et al. analyzed 1,068 patients from 3 UK hospitals and identified these 5 factors as independent predictors of 30-day mortality. The score was later validated in multiple international cohorts totaling more than 12,000 patients, confirming that it is a practical severity summary rather than just a theoretical mnemonic.

Reading the Score as Context

Score 0–1 is associated with low short-term mortality in the original data and often fits lower-acuity management discussions. Score 2 sits in an intermediate zone where inpatient review becomes more common. Scores 3–5 reflect progressively higher mortality and usually push the conversation toward higher-acuity monitoring. Those patterns are useful context, but the score does not issue an admit order by itself.

Limitations of CURB-65

CURB-65 may underestimate severity in younger patients with severe sepsis (who score low on age), patients with hypoxemia but relatively preserved blood pressure, and immunocompromised patients. It does not account for imaging findings, lactate, oxygen requirement, or comorbidity burden. Always read the score alongside the bedside picture rather than in isolation.

Frequently Asked Questions

• What is CURB-65?

  CURB-65 is a clinical prediction rule for community-acquired pneumonia severity, developed by Lim et al. in 2003. It uses 5 bedside parameters (Confusion, Urea, Respiratory rate, Blood pressure, age ≥65) to estimate 30-day mortality and add level-of-care context.

• When should CURB-65 be used?

  CURB-65 is most useful at initial assessment of an adult with community-acquired pneumonia. It helps frame how severe the presentation looks in the original cohorts, but it should sit alongside oxygenation, imaging, comorbidities, and bedside judgment rather than replacing them.

• What is the difference between CURB-65 and CRB-65?

  CRB-65 excludes the urea/BUN criterion, so it can be used without lab results. It scores 0–4 and is often used in outpatient or community settings as a quicker severity screen.

• How does CURB-65 compare to PSI?

  The Pneumonia Severity Index (PSI) uses 20 variables including lab values, comorbidities, and imaging. It may be more accurate for identifying low-risk patients but is more complex. CURB-65 is simpler and preferred for initial bedside assessment. Both are recommended by IDSA/ATS guidelines.

• Can CURB-65 be used for COVID pneumonia?

  CURB-65 was validated for bacterial community-acquired pneumonia and may underestimate severity in COVID-19 pneumonia, which often features rapid respiratory deterioration despite initially stable vital signs. COVID-specific tools (such as 4C Mortality Score) should be preferred for SARS-CoV-2 infections.

• What does "confusion" mean in CURB-65?

  Confusion refers to new-onset mental confusion, typically assessed using the Abbreviated Mental Test Score (AMTS ≤ 8) or any new disorientation to person, place, or time. Pre-existing cognitive impairment (e.g., dementia) should not be counted unless there is acute change from baseline.