CURB-65 Score for Pneumonia Severity

Estimates mortality of community-acquired pneumonia to help determine inpatient vs. outpatient treatment. The CURB-65 calculator also can be used in the emergency department setting to risk stratify a patient’s community acquired pneumonia.


BUN ( blood urea nitrogen) > 19 mg/dl(> 7 mmol/L):

Respiratory Rate ≥30:

Systolic BP < 90 mmHg or Diastolic BP ≤ 60 mmHg:

Age ≥ 65:

Is this a COVID-19 patient?
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Mortality Risk
Recommendation per Derivation Study
0 0 0

The CURB-65 scores range from 0 to 5. Assign points as in the table based on confusion status, urea level, respiratory rate, blood pressure, and age. Clinical management decisions can be made based on the score based on the addition of the selected points:

BUN > 19 mg/dl (> 7 mmol/L)+1
Respiratory Rate ≥ 30+1
Systolic BP < 90 mmHg or Diastolic BP ≤ 60 mmHg+1
Age ≥ 65+1

While many pneumonias are viral in nature, typical practice is to provide a course of antibiotics given the pneumonia may be bacterial.

Disposition (inpatient vs. outpatient) often dictates further care and management — including lab testing, blood cultures, etc.

For patients scoring high on CURB-65, it would be prudent to ensure initial triage has not missed the presence of sepsis. Evaluation of SIRS criteria should be considered.

Score interpretation (as per derivation study):

CURB-65 score30-day Mortality RiskRecommendation per Derivation Study
00.60%Low risk; consider home treatment
12.70%Low risk; consider home treatment
26.80%Short inpatient hospitalization or closely supervised outpatient treatment
314.00%Severe pneumonia; hospitalize and consider admitting to intensive care
4 or 527.80%Severe pneumonia; hospitalize and consider admitting to intensive care

The original study was a retrospective review of three prospective studies of CAP in the UK, New Zealand, and the Netherlands. It included a total of 1068 patients. A five-point score based on confusion, urea, respiratory rate, blood pressure, and age was developed to stratify patients into different treatment group based on mortality risk. The validation study was done in India and included 150 patients.

The CURB-65 Score includes points for confusion and blood urea nitrogen, which in the acutely ill elderly patient, could be due to a variety of factors. An alternative scoring system, SOAR, circumvents those two parameters. It uses low systolic BP and poor oxygenation, advancing age, high respiratory rate.

CURB-65’s original study including co-morbidity variables like chronic lung disease, chronic liver disease, CHF, CVD, and DM, and these were controlled for when developing the relevant criteria for the risk stratification that ultimately led to CURB-65’s risk factors.

Several other more recent validation studies in several different countries show increasing mortality and even need for intubation with increasing CURB-65 scores, ranging from 0-1.1% (CURB-65 score = 0) to 17-60% (CURB-65 score = 5), with over 3100 patients in these studies when combined.


CURB-65 is fast to compute, requires likely already-available patient information, and provides an excellent risk stratification of community acquired pneumonia. It can facilitate better utilization of resources and treatment initiation.

In comparison to the pneumonia severity index, CURB-65 offers equal sensitivity of mortality prediction due to community acquired pneumonia. Notably, CURB-65 (74.6%) has a higher specificity than pneumonia severity index (52.2%).

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  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):377-382. doi:10.1136/thorax.58.5.377
  2. Aujesky D, Auble TE, Yealy DM, Stone RA, Obrosky DS, Meehan TP, Graff LG, Fine JM, Fine MJ. Prospective comparison of three validated prediction rules for prognosis in community-acquired pneumonia. Am J Med. 2005 Apr;118(4):384-92. doi: 10.1016/j.amjmed.2005.01.006. PMID: 15808136.
  3. Shah BA, et. al. Validity of Pneumonia Severity Index and CURB-65 Severity Scoring Systems in Community Acquired Pneumonia in an Indian Setting. The Indian Journal of Chest Diseases & Allied Sciences. 2010;Vol.52.
  4. British Thoracic Society, Myint PK, Kamath AV, Vowler SL, Maisey DN, Harrison BD. Severity assessment criteria recommended by the British Thoracic Society (BTS) for community-acquired pneumonia (CAP) and older patients. Should SOAR (systolic blood pressure, oxygenation, age and respiratory rate) criteria be used in older people? A compilation study of two prospective cohorts. Age Ageing. 2006 May;35(3):286-91. doi: 10.1093/ageing/afj081. PMID: 16638769.
  5. Capelastegui A, España PP, Quintana JM, Areitio I, Gorordo I, Egurrola M, Bilbao A. Validation of a predictive rule for the management of community-acquired pneumonia. Eur Respir J. 2006 Jan;27(1):151-7. doi: 10.1183/09031936.06.00062505. PMID: 16387948.

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