Curb 65 Calculator
Assess community-acquired pneumonia severity using Confusion, Urea, Respiratory rate, BP, and age 65.
Formula
CURB-65 Score = C + U + R + B + 65 (range 0-5)
Each criterion scores 1 point: C = Confusion (new onset), U = Urea > 7 mmol/L (BUN > 19.6 mg/dL), R = Respiratory rate >= 30/min, B = Blood pressure (systolic < 90 or diastolic <= 60 mmHg), 65 = Age >= 65 years. Score range is 0-5 with higher scores indicating greater severity and mortality risk.
Worked Examples
Example 1: Elderly Patient with Moderate Pneumonia
Problem: A 72-year-old patient presents with pneumonia. They are confused (new onset), have a urea of 9 mmol/L, respiratory rate of 24 breaths/min, and blood pressure of 110/70 mmHg.
Solution: Confusion: Yes = 1 point\nUrea > 7 mmol/L: 9 mmol/L = Yes = 1 point\nRespiratory rate >= 30: 24 = No = 0 points\nBP (systolic < 90 or diastolic <= 60): 110/70 = No = 0 points\nAge >= 65: 72 years = Yes = 1 point\nTotal CURB-65 Score: 1 + 1 + 0 + 0 + 1 = 3
Result: CURB-65 Score: 3 (High Risk) | 30-day mortality: ~14% | Recommend: Hospitalization with IV antibiotics
Example 2: Young Adult with Community-Acquired Pneumonia
Problem: A 35-year-old patient presents with cough, fever, and infiltrate on chest X-ray. Alert and oriented, urea 5 mmol/L, respiratory rate 22, blood pressure 125/80 mmHg.
Solution: Confusion: No = 0 points\nUrea > 7 mmol/L: 5 mmol/L = No = 0 points\nRespiratory rate >= 30: 22 = No = 0 points\nBP (systolic < 90 or diastolic <= 60): 125/80 = No = 0 points\nAge >= 65: 35 years = No = 0 points\nTotal CURB-65 Score: 0
Result: CURB-65 Score: 0 (Low Risk) | 30-day mortality: ~0.6% | Recommend: Outpatient treatment with oral antibiotics
Frequently Asked Questions
What is the CURB-65 score and what does it measure?
The CURB-65 score is a clinical prediction rule used to assess the severity of community-acquired pneumonia (CAP) and guide disposition decisions. It was developed by the British Thoracic Society and validated across multiple international studies. The acronym stands for Confusion, Urea greater than 7 mmol/L, Respiratory rate 30 or more breaths per minute, Blood pressure (systolic less than 90 or diastolic 60 or less mmHg), and age 65 or older. Each criterion present adds one point to the score, giving a range from zero to five. Higher scores indicate more severe pneumonia and greater 30-day mortality risk.
How is the CURB-65 score interpreted for clinical decisions?
The CURB-65 score divides patients into three management groups based on their 30-day mortality risk. A score of zero to one indicates low risk with mortality under three percent, and these patients can typically be managed as outpatients with oral antibiotics. A score of two represents moderate risk with approximately seven percent mortality, warranting consideration for short hospital admission or closely supervised outpatient care. Scores of three to five indicate high risk with mortality ranging from 14 to 28 percent, and these patients require hospitalization with intravenous antibiotics, with scores of four or five prompting consideration for intensive care unit admission.
What is the difference between CURB-65 and CRB-65?
CRB-65 is a simplified version of CURB-65 that omits the urea (blood test) component, making it suitable for use in primary care and outpatient settings where laboratory results may not be immediately available. CRB-65 uses only four criteria: Confusion, Respiratory rate, Blood pressure, and age 65 or older, giving a score from zero to four. A CRB-65 score of zero suggests very low risk suitable for home treatment, a score of one to two indicates moderate risk requiring hospital assessment, and a score of three to four indicates high severity requiring urgent hospitalization. CRB-65 is slightly less accurate than CURB-65 but remains a validated and practical tool.
How is confusion defined in the CURB-65 criteria?
In the CURB-65 scoring system, confusion is defined as new-onset mental confusion, specifically an Abbreviated Mental Test Score (AMTS) of 8 or less out of 10, or new disorientation in person, place, or time. The AMTS assesses orientation by asking questions about age, date of birth, current year, current time, location, recognition of two persons, recall of an address, dates of major historical events, and counting backward. It is important to distinguish new confusion from baseline cognitive impairment in elderly patients or those with pre-existing dementia. If baseline mental status is unclear, clinical judgment and collateral information from family members should be used.
What urea level is significant in CURB-65?
The CURB-65 score assigns one point when blood urea nitrogen (BUN) exceeds 7 mmol/L, which is equivalent to approximately 19.6 mg/dL in the units commonly used in the United States. Elevated urea in the context of pneumonia reflects dehydration, renal impairment, or both, and is associated with worse outcomes. The urea criterion helps identify patients with systemic compromise beyond the lungs and is one reason CURB-65 slightly outperforms CRB-65 in predicting mortality. When interpreting urea levels, clinicians should consider baseline renal function and medications such as diuretics or ACE inhibitors that may independently affect urea levels.
Is CURB-65 validated for hospital-acquired pneumonia?
No, the CURB-65 score was specifically developed and validated for community-acquired pneumonia (CAP) only and should not be applied to hospital-acquired pneumonia (HAP), ventilator-associated pneumonia (VAP), or healthcare-associated pneumonia (HCAP). These types of pneumonia have different microbiology, risk factors, and prognostic considerations that are not captured by the CURB-65 criteria. For hospital-acquired infections, other scoring systems such as the APACHE II score or the Clinical Pulmonary Infection Score (CPIS) are more appropriate. Using CURB-65 for non-CAP pneumonia may lead to underestimation of severity and inappropriate management decisions.