Predicting severity of community-acquired pneumonia with AMBU-65/CURB-65 score
Prediction tool to define community acquired pneumonia severity on presentation to hospital, recommended by the British Thoracic Society. 
Research authors: Lim W, van der Eerden MM, Laing R, Boersma W, Karalus N, Town G, Lewis S, and Macfarlane J.
Details Formula Study characteristics Files & References
Model author
Model ID
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MeSH terms
  • Mortality
  • Infections, Community-Acquired
  • Bacterial Pneumonia
  • Model type
    Linear model (Calculation)
    No Formula defined yet
    Condition Formula

    Additional information

    In the assessment of severity in community acquired pneumonia (CAP), the modified British Thoracic Society (mBTS) rule identifies patients with severe pneumonia but not patients who might be suitable for home management. A multicentre study was conducted to derive and validate a practical severity assessment model for stratifying adults hospitalised with CAP into different management groups.

    Data from three prospective studies of CAP conducted in the UK, New Zealand, and the Netherlands were combined. A derivation cohort comprising 80% of the data was used to develop the model. Prognostic variables were identified using multiple logistic regression with 30 day mortality as the outcome measure. The final model was tested against the validation cohort.

    1068 patients were studied (mean age 64 years, 51.5% male, 30 day mortality 9%). Age ⩾65 years (OR 3.5, 95% CI 1.6 to 8.0) and albumin <30 g/dl (OR 4.7, 95% CI 2.5 to 8.7) were independently associated with mortality over and above the mBTS rule (OR 5.2, 95% CI 2.7 to 10). A six point score, one point for each of Confusion, Urea >7 mmol/l, Respiratory rate ⩾30/min, low systolic(<90 mm Hg) or diastolic (⩽60 mm Hg) Blood pressure), age ⩾65 years (CURB-65 score) based on information available at initial hospital assessment, enabled patients to be stratified according to increasing risk of mortality: score 0, 0.7%; score 1, 3.2%; score 2, 3%; score 3, 17%; score 4, 41.5% and score 5, 57%. The validation cohort confirmed a similar pattern.

    A simple six point score based on confusion, urea, respiratory rate, blood pressure, and age can be used to stratify patients with CAP into different management groups.

    Study Population

    Total population size: 1068
    Males: {{ model.numberOfMales }}
    Females: {{ model.numberOfFemales }}

    Categorical characteristics

    Name Subset / Group Nr. of patients
    Age ≥ 65 years 621
    < 65 years 447
    Prior antibiotics Yes 317
    No 751
    Comorbid illnesses Chronic lung disease 375
    Ischemic heart disease/heart failure 197
    Cerebrovascular disease 91
    Diabetes mellitus 107
    Chronic liver disease 11
    Pneumonia Severity Index (PSI) risk class Risk class I 131
    Risk class II 217
    Risk class III 223
    Risk class IV 356
    Risk class V 141
    Predicting severity of community-acquired pneumonia with AMBU-65/CURB-65 score
    Refer to Intended Use for instructions before use
    Evidencio B.V., Irenesingel 19, 7481 GJ, Haaksbergen, the Netherlands
    Notes are only visible in the result download and will not be saved by Evidencio

    Calculated CURB-65/AMBU-65 score: points

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    Outcome stratification

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    Conditional information

    Result interpretation

    How this model should be used:
    The CURB-65/AMBU-65 model is a one step strategy for stratifying patients with CAP into risk groups according to risk of mortality at 30 days.1

    • Patients with CURB-65 scores 0 and 1 are at low risk of mortality (<2%) and might be suitable for management as hospital outpatients or by their general practitioner.
    • Patients with a score of 2 are at intermediate risk of mortality (9%) and should be considered for hospital supervised treatment.
    • Patients with  a score >2 are at high risk of mortality (>19%) and should be treated in hospital. Initial care in an intensive care or high dependency unit may be appropriate in those with the highest scores.
    Although low serum albumin was identified as a strong independent prognostic variable in addition to the CURB score for predicting 30 day mortality, it was not included in the final model as it is not a routinely available test in many hospitals. If serum albumin level is at your disposal, you might consider using a more extended model including serum albumin.

    1. 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):377-82.

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    Calculations alone should never dictate patient care, and are no substitute for professional judgement. See our full disclaimer.

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