CURB-65 score of 1 – what does it mean?

⚠︎ Learning page – classification and study figures only, no treatment recommendation.

In short

A CURB-65 of 1 means that 1 of the 5 criteria is met. In the derivation cohort of Lim et al. (2003), 30-day mortality with 1 point was 3.2%. The validation cohort confirmed a similar pattern.

The figures describe groups in the cited studies, not the risk of an individual person. This page contains no treatment or management recommendation.

How a score of 1 comes about

Each of the five criteria scores 1 point: C – new-onset confusion, U – urea > 7 mmol/l, R – respiratory rate ≥ 30/min, B – systolic BP < 90 or diastolic ≤ 60 mmHg, 65 – age ≥ 65 years.

There are 5 combinations for 1 point:

What the original study describes

Lim et al. derived the score in 2003 from three prospective studies of community-acquired pneumonia from the UK, New Zealand and the Netherlands: 1,068 patients, mean age 64 years, overall 30-day mortality 9%. 80% of the data formed the derivation cohort, the rest was used for validation.

In the derivation cohort, 1 and 2 points were close together at 3.2% and 3%; from 3 points, 30-day mortality rose markedly (17%, 41.5%, 57%).

CURB-65 and CRB-65

The CRB-65 omits urea (0–4 points). With the same findings it therefore equals CURB-65, or is 1 point lower if urea is above 7 mmol/l. The mortality figures on this page apply to CURB-65 only.

All scores at a glance

Score30-day mortality (derivation cohort, Lim 2003)
00.7 %
13.2 %
23 %
317 %
441.5 %
557 %

Calculate it yourself

Enter the criteria in the CURB-65 score (pneumonia) calculator – it runs only in your browser.

FAQ

What does a CURB-65 of 1 mean?▾

1 of 5 criteria is met. In the derivation cohort of Lim et al. (2003), 30-day mortality at this score was 3.2%.

Which urea value counts?▾

The original study uses urea > 7 mmol/l, which is about 42 mg/dl urea or 19.6 mg/dl blood urea nitrogen (BUN).

Does the mortality apply to individual patients?▾

No. The percentages come from the 2003 study cohorts and describe groups, not an individual prognosis.

References

  1. Lim WS et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax 2003;58:377–82. · PubMed · full text (PMC)

Learning page for medical education only: classification and figures reported in the cited sources, no treatment or management recommendation, not for use in patients; not a medical device. Last updated: 10/2026 · Dr. Pascal Bafteh