CURB-65 calculator

What is the CURB-65 score?

CURB-65 is a five-point score for adults with community-acquired pneumonia, published by Lim and colleagues in Thorax in 2003. One point each for Confusion, Urea above 7 mmol/L, Respiratory rate of 30 or more per minute, low Blood pressure (systolic below 90 or diastolic 60 or less mm Hg) and age 65 or older. It was built from three prospective studies in the UK, New Zealand and the Netherlands with 1,068 patients, and it uses only data available at the first hospital assessment.

What are the published death rates for each score?

Table 4 of the 2003 paper gives the 30-day deaths in the derivation cohort of 718 patients: 0: 1 of 137 (0.7%); 1: 4 of 187 (2.1%); 2: 17 of 184 (9.2%); 3: 20 of 138 (14.5%); 4: 26 of 65 (40.0%); 5: 1 of 7 (14.3%). The score of 5 rests on just seven patients, so that figure is not a reliable rate. Grouped as in the paper's flow chart, the mortality was 1.5% for 0 to 1 points (5 of 324), 9.2% for 2 points (17 of 184) and 22% for 3 to 5 points (47 of 210). The abstract of the paper lists different numbers for some scores; we use the table, and the group figures above agree with it.

What does each group mean for treatment?

The paper's flow chart pairs three groups with treatment options. For a score of 0 or 1: low-risk group. the 2003 paper described it as likely suitable for home treatment; this page does not decide where anyone is treated. For 2: intermediate-risk group. the 2003 paper’s flow chart lists hospital-supervised treatment as an option. For 3 or more: high-risk group. the 2003 paper’s flow chart lists hospital care as for severe pneumonia, with intensive care assessment at a score of 4 or 5. The British Thoracic Society guideline for adults with pneumonia (2009) builds on this score; CRB-65 is the version without a blood test. These are aids to judgment: social circumstances, other illnesses, the ability to take tablets and oxygen levels are outside the score.

Do US guidelines recommend CURB-65?

The 2019 ATS/IDSA guideline for community-acquired pneumonia prefers the Pneumonia Severity Index (PSI) over CURB-65 for deciding whether to admit a patient, noting its higher discriminative power for mortality, and says that either tool should be used together with clinical judgment. It reserves direct admission to intensive care for patients needing vasopressors or mechanical ventilation. CURB-65 remains common because it is quick, but it is not the US guideline's first choice.

How is the urea cut-off written in US units?

The paper uses urea above 7 mmol/L. US labs report blood urea nitrogen (BUN) in mg/dL; one mmol/L of urea carries about 2.801 mg/dL of nitrogen, so 7 mmol/L is a BUN of 19.6 mg/dL. This page converts a BUN with that factor and counts the point above the threshold. In the first example below, a BUN of 25 mg/dL is 8.9 mmol/L, which scores. A BUN of 19 mg/dL is 6.8 mmol/L, just under the threshold; a value that close to the line is a judgment call.

What if there is no urea result yet?

Leave the urea box empty. The page then scores the four remaining items as CRB-65, a 0 to 4 version that needs no blood test and is meant for settings such as the doctor's office. Table 4 of the paper reports its own death rates for CRB-65 in the same patients, and the page shows those.

What counts as confusion?

The flow chart in the paper defines it as a Mental Test Score of 8 or less, or new disorientation in person, place or time. The point is for new confusion, not for dementia the person always had. This page takes your yes or no as given; it cannot assess mental state.

How the points add up

Each of the five items is scored 0 or 1, so the score runs from 0 to 5. The threshold values come straight from the paper: a respiratory rate of 30 or more, a systolic pressure below 90 or a diastolic pressure of 60 or lower, and an age of 65 or more, with the urea above 7 mmol/L. Only one of the two blood-pressure numbers needs to be low to earn the point.

Worked example

A 72-year-old is not confused, has a BUN of 25 mg/dL (8.9 mmol/L), breathes 32 times a minute and has a blood pressure of 100/55. The urea, breathing, diastolic pressure and age each earn a point: 4 of 5, which is in the high-risk group. A 58-year-old with a BUN of 5 mmol/L, 22 breaths a minute and 128/78 scores 0. A 70-year-old with the same vitals but no urea result is scored as CRB-65: 1 of 4, from age alone.

Limits of this method

The score was derived in hospital patients in three countries, and the authors note that the health systems differ from those in the USA. It does not include oxygen saturation, chest X-ray findings, other illnesses or whether the person lives alone, and the ATS/IDSA guideline weighs these through clinical judgment and the PSI. Death rates come from patients in a study published in 2003 and may not match current care. The rate at a score of 4 is based on 65 patients and at 5 on seven.

Common mistakes

An easy slip is entering the lab urea in the wrong unit: a BUN of 20 mg/dL is not 20 mmol/L. Another is comparing a CRB-65 result with the CURB-65 death rates, which come from a different table. Finally, a low score is not an instruction to send a patient home; the paper itself describes the options as ones that “might be suitable.”

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;58:377–382 (Table 4 and Figure 2); 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; Metlay JP, Waterer GW, Long AC, et al., “Diagnosis and treatment of adults with community-acquired pneumonia,” Am J Respir Crit Care Med 2019;200:e45–e67. Related: mean arterial pressure, Glasgow Coma Scale, blood pressure calculator.

For general information only — not medical advice, and not a tool for patient care decisions. Talk with a doctor or call emergency services about anyone you are worried about. How we check our calculators.