British Thoracic Society Community Acquired Pneumonia Severity Calculations and Guidelines ("CURB-65")

This severity calculation is based on the presence or absence of five parameters, are derived from Thorax 2003;58:37, and are suggested for use in the 2009 BTS update to the guidelines:

  1. Confusion (new disorientation in person, time or place), or more formally, a score less than 9 in a Mini Mental Status exam (from 2009 BTS guidelines):
    1 point each for a correct answer to the following questions:
    Time to nearest hour
    Hospital name
    Recognition of two persons (e.g. doctor, nurse)
    Recall of home address
    Year of important and well known historical event (e.g. end of WWII)
    Name of important figure (e.g. President of country)
    Count backwards from 20 to 1
  2. Elevation of blood Urea, or blood urea nitrogen (BUN) level above 7 mmol/L (urea) or 20 mg% (BUN)
  3. Respiratory rate >= 30 breaths/min
  4. Low Blood pressure, < 90 mm Hg systolic OR =<60 mm Hg diastolic
  5. Age >= 65 years

One point is awarded to each element present, for a total possible maximum score of 5

score 0 1 2 3 4 5
predicted mortality (%)# 0.01 1.7 9 16 37 20*

# based on validation and derivation cohorts - from Thorax 2003-58-37

* low numbers and very broad confidence interval


BTS reccomendations for hospital admission based on severity score:

  • Score 0: " low risk of death ... do not normally require hospitalisation for clinical reasons"
  • Score 1 or 2: " increased risk of death and hospital referral and assessment should be considered, particularly with Score 2"
  • Score >=3: "high risk of death and require urgent hospital admission"

For assesment in hospital, the BTS recommends the following actions based on score

  • Score 0 or 1: " Low risk of death. They can be treated as having non-severe pneumonia and may be suitable for home treatment"
  • Score 2 : "Increased risk of death. They should be considered for short stay inpatient treatment or hospital supervised outpatient treatment. This decision is a matter of clinical judgement"
  • Score >=3: " High risk of death. They should be managed as having severe pneumonia, be seen promptly by a senior physician, and considered to have high severity pneumonia. Those with scores >3 should be considered for ICU admission.

The BTS guidelines caution that clinical judgement is required in the interpretation of these guidelines, and that considerations be given to social circumstances regarding care at home. They also suggest that young patients with a low severity score could in fact have severe pneumonia, as in the example of a non-confused 30 year old with a score of 1 due to a respiratory rate of 40, but with normal BUN and blood pressure.

There is also an abbreviated "CRB-65" scoring system, which does not require laboratory testing, and can therefore be used more easily in the outpatient setting. It differs from CURB-65 in that blood urea (or BUN) measurement is not included in the scoring system. The predicted mortality is shown below for CRB-65 scores (see CURB-65 table for source and notes).

score 0 1 2 3 4
predicted mortality (%) # 0.9 5.2 12.0 32.4 25*
# based on validation and derivation cohorts - from Thorax 2003-58-37

* low numbers and very broad confidence interval


Some personal caveats:

  • The "Fine" PSI scoring system uses similar scoring parameters, and is acknowledged not to be perfect in several studies - see the BTS guidelines for a discussion of this. Some patients with low scores end up having severe disease.
  • Taking into account patient oxygenation and other patient factors may help better define risk, and has been shown to be very useful in a recent prospective study of treatment of mild severity pneumonia

written by Paul Edelstein Feb 2005, revised Feb 2011, links updated 3/24/2013

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