Curb 65 Calculator

CURB-65 answers a disposition question rather than a diagnostic one: given that this adult has community-acquired pneumonia, how likely are they to die within 30 days, and can they be sent home. Each of five findings scores 1 point. Confusion means new disorientation or an Abbreviated Mental Test Score of 8 or less out of 10, which must be distinguished from established dementia. Urea above 7 mmol/L, equivalent to a blood urea nitrogen above about 19.6 mg/dL, flags dehydration or renal hypoperfusion. A respiratory rate of 30 or more per minute and a blood pressure with systolic below 90 or diastolic 60 or less identify respiratory and circulatory failure. Age 65 or over is included because age independently predicts death even after physiological variables are accounted for. Reported 30-day mortality climbs steeply with the total, from well under 1 percent at 0 to a few percent at 1, around 7 percent at 2, roughly 14 percent at 3, and above 25 percent at 4 or 5. The corresponding management bands are outpatient treatment at 0 to 1, short admission or supervised outpatient care at 2, and hospital admission with consideration of critical care at 3 or more. The rule was derived and validated only for community-acquired pneumonia and should not be applied to hospital-acquired or ventilator-associated infection. It captures no comorbidity, no oxygen saturation, and no radiographic extent, so it tends to underestimate severity in a young hypoxaemic patient with bilateral consolidation, and it says nothing about whether a patient can safely manage at home. CRB-65 drops the urea term for settings without immediate bloods.

British Thoracic Society guidance from the late 1980s already used a simple three-variable rule combining respiratory rate, diastolic hypotension, and raised urea to identify severe pneumonia, but it performed inconsistently and omitted the two strongest and simplest predictors, confusion and age. Wei Shen Lim and the British Thoracic Society research committee rebuilt the rule using pooled prospective cohorts of adults admitted with community-acquired pneumonia in the United Kingdom, New Zealand, and the Netherlands, and published CURB-65 in Thorax in 2003 along with the reduced CRB-65 variant for primary care. The competing instrument was the Pneumonia Severity Index, developed by Michael Fine and colleagues from the Pneumonia Patient Outcomes Research Team and published in the New England Journal of Medicine in 1997 using data from more than 14,000 patients. PSI is more accurate at identifying genuinely low-risk patients, but it requires 20 variables and a two-step algorithm, which limited bedside use. CURB-65 spread rapidly precisely because it could be worked out from five items already recorded during triage, and it was written into British and European pneumonia guidelines and into many emergency department pathways. Later guidance has tempered its role: the 2019 American Thoracic Society and Infectious Diseases Society of America guideline prefers PSI for the admission decision, and both bodies stress that any severity score supplements rather than replaces clinical judgement about oxygenation, comorbidity, and social circumstances.