This CURB-65 pneumonia severity score calculator is a risk stratification and prediction tool based on clinical determinations such as respiratory rate. Discover more about the model, its interpretation and some medical significations of Community Acquired Pneumonia (CAP).


Blood Nitrogen Urea >19 mg/dL (> 7 mmol/L)

Respiratory rate equal to or higher than 30/min

Systolic BP <90 mmHg or Diastolic BP <=60 mmHg

Age equal or higher than 65

How does this CURB-65 pneumonia severity score calculator work?

This health calculator provides a useful tool for all clinicians interested to risk stratify patients with community acquired pneumonia based on five clinical determinations and an interpretation comprising of a 30 days mortality risk prediction.

The CURB-65 is a model that has been adapted after a research by Lim, a study that took place in the UK, the Netherlands and New Zealand that aimed to validate the previous Pneumonia Severity Index (PSI) and discover whether there are other connections between mortality and clinical determinations. The acronym in the CURB-65 severity score calculator comes from the usage of the determinations presented below:

Confusion – presence of delirium or confusion.

Urea - Blood Nitrogen Urea >19 mg/dL (> 7 mmol/L) – different meanings because of the acute illness setting.

Respiratory rate equal to or higher than 30/min.

Blood pressure: Systolic BP <90 mmHg or Diastolic BP <=60 mmHg.

■ Age equal or higher than 65 – this age being considered the cut off for various risks and complications that are said to change mortality risk.

Although the above factors are very straight forward and can easily be interpreted to provide the overall score, every study that cites the original one states that clinical decision making should still be above all scoring, regardless of the risk stratification model used.

An important point of CURB-65 is that is very specific and can identify need for ICU intensive care unit, at a similar level with the predecessor PSI model. However, one of the criticisms received by the study is due to the fact that there isn’t any consideration given to comorbidities that are very often, especially given the advanced age in some subjects.

CURB-65 interpretation

As a clinical prediction rule, this model has been validated in several setting and is also recommended by the British Thoracic Society in the severity assessment of acute pneumonia cases.

The main benefit of this model is that not only provides a treatment route for community acquired pneumonia cases and whether they need admission in the ICU but also a prognostic value for the following month.

Each of the five factors is awarded either 0 points in case of a no answer or 1 point in case of a yes answer. The overall CURB-65 score therefore ranges between 0, meaning no risk pneumonia if diagnosed and 5 which is indicative of very severe pneumonia.

In the case of cumulative scores of 0 or 1, outpatient treatment is advisable as the mortality risk is less than 3% in 30 days. Scores of 2 require more assistance and might need hospital admission and also the risk grows exponentially. At scores above 3, pneumonia is considered to be of increasing severity and careful monitoring is compulsory.

Score Mortality risk Interpretation Recommendations
0 0.60% Low risk pneumonia Outpatient treatment
1 2.70% Low risk pneumonia Outpatient treatment, less likely inpatient
2 6.80% Moderate risk pneumonia Short inpatient stay or supervised outpatient treatment
3 14% Severe risk pneumonia Serious hospitalization
4 27.80% Severe risk pneumonia Serious hospitalization, possibly ICU
5 27.80% Severe risk pneumonia Serious hospitalization, possibly ICU

Community acquired pneumonia CAP – medical considerations

This is a common infectious illness with high admission rates and associated with high morbidity and mortality risks, especially in elderly patients. Severity ranges but initial assessment and treatment are vital in reducing the above mentioned risks and also in avoiding unnecessary procedures or hospitalization in cases that are deemed to be low risk.

The bacterial pathogens most likely causing this type of pneumonia are Streptococcus pneumonia, and Haemophilus influenza and the infection is produced through inhalation of the pathogens in one of the lung segments or in the lobes.

Severe cases are also placed with other comorbidities such as cardiopulmonary disease or impaired splenic function. Symptoms include fever, cough, mild dyspnea, localized chest pain and general malaise and sometimes are accompanied by gastro intestinal symptoms such as nausea or diarrhea.


1) Lim W, van der Eerden M, Laing R, Boersma W, Karalus N, Town G, Lewis S, Macfarlane J. (2003) Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax; 58(5): 377–382.

2) Torralba MA, Amores-Arriaga B, Olivera S, Perez-Calvo JI. (2010) Validity of Fine and CURB scales in the treatment of community-acquired pneumonia in adults. Med Clin (Barc); 135(13):624-5.

3) Howell MD, Donnino MW, Talmor D, Clardy P, Ngo L, Shapiro NI. (2007) Performance of severity of illness scoring systems in emergency department patients with infection. Acad Emerg Med; 14(8):709-14.

19 Aug, 2015