What are the criteria for determining low, medium, and high risk levels in patients with pneumonia, considering factors such as age, co-morbidities, vital signs, confusion, urea levels, respiratory rate, blood pressure, and impaired renal function?

Pneumonia Risk Stratification Using CURB-65

Use the CURB-65 score to stratify pneumonia patients into low, medium, and high risk categories based on mortality risk and guide site-of-care decisions. 1

CURB-65 Scoring Components

The CURB-65 system assigns one point for each of the following five criteria present at evaluation: 2, 1

• Confusion (mental test score <8, or new disorientation to person, place, or time)
• Urea >7 mmol/L (or BUN >19 mg/dL)
• Respiratory rate ≥30 breaths/min
• Blood pressure (systolic <90 mmHg or diastolic ≤60 mmHg)
• 65 years of age or older

Risk Level Classification and Management

Low Risk: CURB-65 Score 0-1

• Mortality risk: 0.7-2.1% 2, 1
• Management: Outpatient treatment with oral antibiotics is appropriate for most patients 1, 3
• These patients can safely be managed at home without hospitalization 2

Medium Risk: CURB-65 Score 2

• Mortality risk: 9.2% 2, 1
• Management: Consider short-stay inpatient treatment or hospital-supervised outpatient treatment 2
• This decision requires clinical judgment and consideration of additional factors such as ability to maintain oral intake, social support, and comorbidities 3
• Patients in this category face significantly elevated mortality risk and may require hospitalization or intensive in-home health services 3

High Risk: CURB-65 Score 3-5

• Mortality risk: Score 3 = 14.5%, Score 4 = 40%, Score 5 = 57% 2, 1, 3
• Management: Hospital admission with prompt evaluation for ICU care 2, 1, 3
• Patients with scores of 4-5 should be considered for high dependency unit (HDU) or intensive care unit (ICU) transfer 2
• These patients require active intervention for physiologic derangements 3

Special Considerations and Pitfalls

When CURB-65 May Underestimate Severity

Young patients (<65 years) with severe respiratory failure may have their risk underestimated because age is heavily weighted in the scoring system, despite significant physiologic derangement. 1, 3

Bilateral lung infiltrates on chest radiography consistent with primary viral pneumonia should be managed as severe pneumonia regardless of CURB-65 score. 2

Additional Factors Requiring Hospitalization Despite Low Scores

Consider hospitalization even with CURB-65 scores 0-1 if any of the following are present: 3

• Inability to maintain oral intake
• Homelessness or lack of social support
• Severe psychiatric illness
• Failure of prior adequate outpatient antibiotic therapy
• Important comorbidities (HIV, severe COPD, immunosuppression)

ICU Admission Decisions

CURB-65 alone performs poorly for predicting ICU needs. 1, 3 For ICU triage decisions, use the IDSA/ATS severe CAP criteria instead, which have higher sensitivity (78.4%) for predicting critical care interventions. 1

Direct ICU admission is required regardless of CURB-65 score for: 1, 3

• Septic shock requiring vasopressors
• Acute respiratory failure requiring intubation and mechanical ventilation

Consider ICU admission for patients with ≥3 minor IDSA/ATS criteria: respiratory rate ≥30/min, PaO2/FiO2 ratio ≤250, multilobar infiltrates, confusion, uremia, leukopenia, thrombocytopenia, hypothermia, or hypotension requiring aggressive fluid resuscitation. 1

Simplified Alternative: CRB-65

A simplified version (CRB-65) omits the urea/BUN measurement and can be used in outpatient settings or resource-limited environments where laboratory testing is not readily available. 2, 1, 3 This gives a point range from 0 to 4 rather than 0 to 5. 3

Comparison with Pneumonia Severity Index (PSI)

The PSI is more complex, incorporating 20 variables, but has similar effectiveness in predicting mortality. 2, 4 The PSI stratifies patients into five risk classes (I-V), with classes I-III suitable for outpatient treatment and classes IV-V typically requiring hospitalization. 2, 4 However, CURB-65 is preferred for its simplicity and ease of use in emergency settings, requiring only one laboratory test (urea/BUN) compared to multiple laboratory values for PSI. 1, 3 Recent meta-analysis shows CURB-65 has slightly better sensitivity (96.7%) and specificity (89.3%) in predicting admission to intensive care support. 5

Implementation Best Practices

Use CURB-65 as an adjunct to clinical judgment, not as the sole determinant for site-of-care decisions. 1, 3 Implement it as part of a systematic pneumonia care bundle including pulse oximetry and point-of-care lactate measurement. 1, 3

For patients with CURB-65 scores ≥3, promptly evaluate for potential ICU admission to ensure timely and appropriate care. 1, 3

Clinical improvement should be expected within 3 days; patients should contact their physician if no improvement occurs, and reassessment for treatment failure, resistant organisms, or complications is warranted if fever persists beyond 72 hours. 3