# CURB-65 Pneumonia Severity Calculator
> Free CURB-65 calculator for community-acquired pneumonia severity and disposition. Score + 30-day mortality band + inpatient/outpatient guidance. Based on Lim 2003 + IDSA/ATS 2019. Clinician decision support.

## Overview

CURB-65 is a five-point clinical-prediction rule for severity and 30-day mortality in community-acquired pneumonia. The IDSA/ATS 2019 CAP guideline references CURB-65 (alongside the Pneumonia Severity Index) as a validated tool to support disposition decisions. Each component contributes one point: confusion, blood urea nitrogen above 19 mg/dL (urea > 7 mmol/L), respiratory rate at least 30, low blood pressure (SBP < 90 or DBP ≤ 60), and age 65 or above. Lower scores often align with outpatient management; higher scores increasingly favour inpatient and ICU evaluation.

## Who this is for

- Emergency physicians and hospitalists deciding admission vs outpatient
- Internal medicine residents on inpatient pneumonia care
- Primary care clinicians evaluating pneumonia severity

## How to interpret the result

| Score / band | Meaning |
|---|---|
| 0–1 | Low (~0.7–2.1% 30-day mortality) — outpatient often appropriate. |
| 2 | Moderate (~9.2%) — short admission or supervised outpatient commonly considered. |
| 3 | High (~14.5%) — admission typically warranted. |
| 4–5 | Very high (~40–57%) — ICU evaluation commonly considered. |

## Cited source

**IDSA / ATS 2019 Diagnosis and Treatment of Adults with CAP** (2019) — IDSA / ATS

_Primary publication:_ Lim WS et al., Thorax 2003 (CURB-65 derivation)

## FAQs

### When is CURB-65 preferred over PSI?

CURB-65 is faster to apply (five binary inputs) and is widely used in emergency department triage. PSI is more granular (20 inputs) and may better discriminate low-risk patients. The IDSA/ATS 2019 CAP guideline accepts either.

### Does CURB-65 dictate ICU admission?

No. CURB-65 ≥ 3 supports considering ICU evaluation, but the 2019 IDSA/ATS guideline lists explicit major and minor severe-CAP criteria that more directly inform ICU disposition.

### Can I use CURB-65 in nursing-home pneumonia?

CURB-65 was derived in CAP, not nursing-home or hospital-acquired pneumonia. Use HCAP/HAP/VAP criteria and institutional protocols for those populations.

### What if BUN is unavailable?

CRB-65 (without urea) can be used as a simplified version when laboratory data is unavailable, e.g. in primary care. Performance is slightly reduced but it remains useful.

### Is CURB-65 score 2 always an admission?

Not by rule. CURB-65 is decision support; clinicians integrate oxygenation, social factors, comorbid burden, and access to follow-up before disposition.

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_Rounds AI is a citation-first clinical AI assistant. It supports clinical reasoning by surfacing cited information and is not a substitute for independent clinical judgement._