CRB-65
Mortality risk and treatment setting in community-acquired pneumonia — no blood test needed
- AWMF S3 Pneumonie 2021
Sources last checked: 2026-10-13
CRB-65
Mortality risk and treatment setting in community-acquired pneumonia — no blood test needed
30-day mortality 0 % in the German CAPNETZ cohort (2 % in hospitalised patients, German quality-assurance data). AWMF S3 2021 provides for outpatient treatment if the patient is clinically stable, SpO₂ > 92 % without new desaturation, with no unstable comorbidity, no complication and no social reason for admission, with re-evaluation after 48–72 h.
A low score never overrides the bedside picture: hypoxaemia (SpO₂ ≤ 92 %), unstable comorbidity, complications such as pleural effusion or social factors can require admission at CRB-65 = 0. It discriminates poorly in nursing-home residents and bedbound patients.
Interpretation
| 0 — low risk | 30-day mortality 0 % in the German CAPNETZ cohort (2 % in hospitalised patients, German quality-assurance data). AWMF S3 2021 provides for outpatient treatment if the patient is clinically stable, SpO₂ > 92 % without new desaturation, with no unstable comorbidity, no complication and no social reason for admission, with re-evaluation after 48–72 h. |
|---|---|
| 1–2 — increased risk | Mortality ≈ 6 % (CAPNETZ) to 13 % (hospitalised patients). AWMF S3 2021 no longer regards outpatient treatment as the default in this group; the guideline provides for an assessment of hospital admission that includes oxygenation and comorbidities. |
| 3–4 — high risk | Mortality ≈ 23 % (CAPNETZ) to 34 % (hospitalised patients). AWMF S3 2021 provides for hospital admission in this group, with prompt assessment for organ dysfunction, sepsis and the need for intensive care. |
What is the CRB-65?
CRB-65 estimates the 30-day mortality of community-acquired pneumonia from four bedside findings: confusion, respiratory rate, blood pressure and age. It is CURB-65 (Lim, Thorax 2003) without the urea value, and was validated for both outpatients and inpatients in the German CAPNETZ network (Bauer, J Intern Med 2006). The German AWMF S3 guideline 2021 uses it as the objective aid for deciding on outpatient versus hospital treatment.
When to use it
- Adults with clinically or radiologically diagnosed community-acquired pneumonia in general practice or the emergency department.
- Deciding, together with oxygenation and comorbidities, whether outpatient treatment is safe.
- Where no blood test is available — the main advantage over CURB-65.
- Re-assessing patients whose condition changes in the first days of treatment.
When not to use it
- Hospital-acquired or ventilator-associated pneumonia, or severely immunosuppressed patients.
- Nursing-home residents or chronically bedbound patients, in whom the score no longer identifies a low-risk group.
- As the only criterion for intensive care — ATS/IDSA minor/major criteria and sepsis assessment address that question.
How it is calculated
| Criterion | Points |
|---|---|
| Confusion (new disorientation to person, place or time) | +1 |
| Respiratory rate ≥ 30 /min | +1 |
| Systolic BP < 90 mmHg or diastolic BP ≤ 60 mmHg | +1 |
| Age ≥ 65 years | +1 |
Clinical pearls and limitations
- A low score never overrides the bedside picture: hypoxaemia (SpO₂ ≤ 92 %), unstable comorbidity, complications such as pleural effusion or social factors can require admission at CRB-65 = 0. It discriminates poorly in nursing-home residents and bedbound patients.
- AWMF S3 2021: CRB-65 = 0 supports outpatient care only together with SpO₂ > 92 %, no unstable comorbidity, no complication and adequate home support.
- The AWMF S3 guideline includes oxygenation in the assessment of every patient — pulse oximetry in practice, blood gas in the ED. Hypoxaemia was the commonest reason for admission despite a low score.
- Confusion means new disorientation, not known dementia.
- AWMF S3 2021 provides for re-evaluation after 48–72 hours, the window in which deterioration typically occurs.
- Systolic < 90 OR diastolic ≤ 60 mmHg — either one scores the point.
Frequently asked questions
What is the difference between CRB-65 and CURB-65?
CURB-65 adds one point for urea > 7 mmol/L. CRB-65 drops the lab value so it can be used in general practice; prognostic accuracy is comparable in German data.
Can a patient with CRB-65 = 0 always go home?
No. The German guideline also requires adequate oxygenation (SpO₂ > 92 %), no unstable comorbidity, no complication such as pleural effusion and no social reason for admission.
What mortality does a CRB-65 of 1–2 mean?
About 6 % in the CAPNETZ study population and about 13 % among hospitalised patients in German quality-assurance data.
Does age ≥ 65 alone justify admission?
Not on its own. The guideline asks for age to be judged together with comorbidity, functional status and the social situation.
Evidence and guidelines
- Primary source: Bauer TT, Ewig S, Marre R, Suttorp N, Welte T; CAPNETZ Study Group. CRB-65 predicts death from community-acquired pneumonia. J Intern Med 2006;260(1):93-101.
- Ewig S, Kolditz M, Pletz M et al. S3-Leitlinie Behandlung von erwachsenen Patienten mit ambulant erworbener Pneumonie – Update 2021. AWMF-Register 020-020 (DGP, PEG, DGI, DGIIN, DEGAM, ÖGP, SGP u. a.).
- Lim WS et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax 2003;58(5):377-382.
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Ask Medelix about the CRB-65Related calculators
- CURB-65Severity and site of care in community-acquired pneumonia
- qSOFABedside alert for poor outcome in suspected infection
- NEWS2National Early Warning Score 2 — detecting clinical deterioration in adults (SpO₂ scale 1)
- SOFA scoreSequential (Sepsis-related) Organ Failure Assessment — organ dysfunction for the Sepsis-3 definition
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