For healthcare professionals
CURB-65 Pneumonia Severity Score
Systolic blood pressure (top number), Diastolic blood pressure (bottom number), Age
Severity of community-acquired pneumonia and 30-day mortality risk.
CRB-65 Pneumonia Score (no blood test)
CURB-65 without urea, for use in the community.
For healthcare professionals / clinical use. Not a self-diagnosis tool.
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Methodology
CRB-65 (BTS 2009; NICE NG250)
1 point each: Confusion, RR ≥ 30, BP (SBP < 90 or DBP ≤ 60), age ≥ 65
Recommended by BTS and NICE for assessing pneumonia severity outside hospital.
- Who it is for
- Adults with community-acquired pneumonia in primary care.
- Version
- 1.0.1
How this calculator works
Where the formula comes from
- CRB-65 is CURB-65 without the blood urea item; CURB-65 was derived by Lim and colleagues (2003) in 1,068 patients from the UK, New Zealand and the Netherlands, with 30-day mortality as the outcome.[1]
The inputs
- One point each for confusion (abbreviated mental test score 8 or less, or new disorientation in person, place or time), respiratory rate 30/min or more, diastolic blood pressure 60 mmHg or less or systolic below 90 mmHg, and age 65 or over (score 0–4).[2]
Versions and alternatives
- CURB-65 adds urea over 7 mmol/L as a fifth item for use in hospital.[1]
Where accuracy falls (published evidence)
- A 2010 meta-analysis of 14 validation studies found that CRB-65 performed well in hospitalised patients but over-predicted 30-day mortality in community settings across all risk groups, and advised caution in general practice.[3]
- In patients with pneumonia and immunosuppression, CRB-65 had limited prognostic accuracy (2020 study).[4]
What guidelines say
- NICE (NG250) recommends CRB-65 in primary care to stratify 30-day mortality risk: 0 low (under 1%), 1–2 intermediate (1–10%) and 3–4 high (over 10%).[2]
- NICE advises using clinical judgement together with CRB-65, bearing in mind that it can be affected by other factors such as comorbidities or pregnancy.[2]
Sources
- Lim WS, van der Eerden MM, Laing R, et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax. 2003;58(5):377–382. doi:10.1136/thorax.58.5.377
- National Institute for Health and Care Excellence. Pneumonia: diagnosis and management (NG250). London: NICE; 2025. https://www.nice.org.uk/guidance/ng250
- McNally M, Curtain J, O'Brien KK, Dimitrov BD, Fahey T. Validity of British Thoracic Society guidance (the CRB-65 rule) for predicting the severity of pneumonia in general practice: systematic review and meta-analysis. Br J Gen Pract. 2010;60(579):e423–e433. PMID 20883616
- Limited prognostic accuracy of the CRB-65 and qSOFA in patients presenting with pneumonia and immunosuppression. Eur J Intern Med. 2020;81:76–81. doi:10.1016/j.ejim.2020.08.006
Compiled from the published sources above. Every statement was agreed independently by three AI research tools (Claude, ChatGPT, DeepSeek) and its source verified in PubMed or Crossref by the Hakeemly editorial team. Not reviewed by a doctor unless stated. Agreed on
Worked example: how to calculate CRB-65
Inputs
- New confusion
- No
- Respiratory rate
- 20 breaths/min
- Systolic blood pressure (top number)
- 120 mmHg
- Diastolic blood pressure (bottom number)
- 75 mmHg
- Age
- 40 years
Result
- CRB-65
- 0 of 4
0: low risk (under 1%)
An illustration with sample values, worked out with the same method the tool above uses.
Limitations
- Prognostic accuracy was limited in patients with immunosuppression (2020 study); use with clinical judgement (NICE NG250).
References
- Lim WS, Baudouin SV, George RC, et al. BTS guidelines for the management of community acquired pneumonia in adults: update 2009. Thorax. 2009;64(Suppl 3):iii1–iii55. doi:10.1136/thx.2009.121434
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