Understanding the CURB-65 Severity Score: A Guide for Assessing Pneumonia Risk


The CURB-65 score is a clinical tool used by healthcare professionals to assess the severity of community-acquired pneumonia (CAP) and guide decisions regarding the need for hospitalization and the intensity of care required. It stands for Confusion, Urea, Respiratory rate, Blood pressure, and age 65 or older, encompassing five critical factors that help predict the mortality risk associated with pneumonia.

Components of the CURB-65 Score

The CURB-65 score is a comprehensive tool used to evaluate the severity of community-acquired pneumonia (CAP) in patients, guiding treatment decisions and determining the need for hospitalization. Each of the five components addresses a critical aspect of the patient’s condition, contributing to an overall assessment of risk.

For an easy calculation, you can use our CURB-65 Severity Score Calculator.


The first component of the CURB-65 score is the assessment of new-onset confusion. This symptom can be a sign that pneumonia is affecting the brain, either through reduced oxygen levels or systemic infection that has progressed to sepsis. Healthcare professionals determine confusion using specific mental status tests, such as the Mini-Mental State Examination (MMSE) or the Confusion Assessment Method (CAM). Alternatively, clinical observation and patient history can also indicate changes in mental status. Confusion in pneumonia patients is a serious sign that the infection is impacting cognitive function, often indicating a more severe course of illness.


The second component involves measuring blood urea nitrogen (BUN) levels. Elevated urea levels (above 7 mmol/L) can signal that the kidneys are under stress or not functioning properly, possibly due to the infection. Urea is a waste product formed in the liver and excreted by the kidneys. High BUN levels suggest that the body is experiencing significant stress, potentially due to dehydration, decreased renal perfusion, or a direct impact of the infection on kidney function. Monitoring urea levels provides insight into the systemic effects of pneumonia, highlighting the need for more intensive treatment and monitoring.

Respiratory Rate

The third criterion examines the patient’s respiratory rate. A rate of 30 breaths per minute or more is a critical indicator of respiratory distress. This high respiratory rate suggests that the patient is struggling to breathe, a common symptom of severe pneumonia where the lungs are unable to adequately exchange oxygen and carbon dioxide. Tachypnea, or rapid breathing, is a response to hypoxia (low oxygen levels) and can be an early sign of respiratory failure. Accurate measurement and continuous monitoring of the respiratory rate are essential for assessing the severity of pneumonia and the need for escalated care.

Blood Pressure

The fourth component assesses blood pressure, specifically looking for a systolic pressure less than 90 mmHg or a diastolic pressure of 60 mmHg or less. Hypotension (low blood pressure) indicates that the cardiovascular system is compromised, which can occur in severe infections. This can be due to septic shock, where the infection causes a systemic inflammatory response leading to widespread vasodilation and decreased blood pressure. Low blood pressure reduces organ perfusion, increasing the risk of organ failure. Regular monitoring and prompt management of hypotension are crucial in patients with severe pneumonia.

Age 65 or Older

The final factor in the CURB-65 score is the patient’s age. Individuals who are 65 years old or older are at a higher risk for complications and mortality from pneumonia. This increased risk is due to several factors, including a decline in immune function with age, the presence of multiple comorbidities, and decreased physiological reserves. Older patients may not present with typical symptoms, making early diagnosis and treatment more challenging. Age is therefore a significant factor in the CURB-65 score, guiding clinicians to adopt a more cautious approach in managing older adults with pneumonia.

Calculating and Interpreting the CURB-65 Score

Each of the five components of the CURB-65 score is assigned one point if present. The total score can range from 0 to 5, with higher scores indicating more severe illness and a higher risk of mortality.

  • Score 0-1: Patients with a score of 0 or 1 are considered low risk. These individuals can often be managed safely as outpatients with oral antibiotics and close follow-up. They typically have a good prognosis and are less likely to experience severe complications.
  • Score 2: A score of 2 suggests moderate risk. Hospitalization should be considered for these patients, depending on the overall clinical picture and social circumstances. This group may benefit from more intensive monitoring and intravenous antibiotics to ensure a favorable outcome.
  • Score 3-5: Patients with scores ranging from 3 to 5 are at high risk and typically require hospitalization. In some cases, admission to an intensive care unit (ICU) may be necessary, especially if the patient is experiencing severe respiratory distress, hypotension, or multi-organ dysfunction. Prompt, aggressive treatment is essential to reduce mortality in this high-risk group.

The CURB-65 score is a valuable tool for clinicians, helping to stratify patients based on the severity of their illness and guide appropriate treatment strategies. It enhances decision-making, ensuring that patients receive the care they need based on their individual risk factors.

Clinical Implications

The CURB-65 score is a valuable tool for guiding treatment decisions and ensuring that patients with community-acquired pneumonia receive appropriate care based on their severity of illness. By stratifying patients into risk categories, healthcare providers can make more informed decisions about the level of care required, potentially improving outcomes and optimizing the use of healthcare resources.

In practice, the CURB-65 score should be used alongside clinical judgment, considering other factors such as the patient’s overall health, comorbid conditions, and social support systems. It is a quick and practical tool that enhances the assessment process, leading to better management of pneumonia in various healthcare settings.