What is the recommended approach for determining pneumonia severity risk score and guiding treatment decisions?

Pneumonia Severity Risk Score Assessment and Treatment Guidance

The 2007 IDSA/ATS severe CAP criteria is recommended over other published scores for assessing pneumonia severity and guiding treatment decisions, as it uses readily available severity parameters and is more accurate than other scores for identifying patients requiring intensive care. 1

Primary Assessment Tools

• The Pneumonia Severity Index (PSI) and CURB-65 are the two most widely validated and recommended severity assessment tools for community-acquired pneumonia (CAP) 1, 2
• PSI stratifies patients into 5 mortality risk classes and is primarily designed to identify low-risk patients who can be safely treated as outpatients 1, 3
• CURB-65 includes five variables: Confusion, Urea nitrogen, Respiratory rate, Blood pressure, and age ≥65 years, making it simpler to calculate than PSI with only 5 variables vs. 20 2, 3
• CRB-65, a simplified version of CURB-65 that omits blood urea nitrogen testing, is useful in settings where blood tests are not readily available 2

PSI Scoring and Risk Stratification

• PSI incorporates 20 variables across several domains: demographics, comorbidities, vital signs, laboratory values, radiographic findings, and oxygenation parameters 1, 3
• Risk classification is determined by point totals: Class I (age <50, no comorbidity, no vital sign abnormalities), Class II (≤70 points), Class III (71-90 points), Class IV (91-130 points), and Class V (>130 points) 1
• PSI risk classes correspond to the following mortality risks: Classes I-III (≤3%), Class IV (8%), Class V (35%) 1, 3

CURB-65 Scoring and Risk Stratification

• CURB-65 scoring interpretation: 0-1 points, consider outpatient treatment; 2 points, consider hospital admission; ≥3 points, consider ICU admission 2
• CURB-65 is easier to interpret at the point of care compared to PSI 2

Treatment Decision Algorithm

1. Calculate both PSI and CURB-65 scores for all patients with suspected CAP 1, 2
2. For outpatient vs. hospitalization decisions:
   • PSI classes I-II patients should be treated as outpatients 1, 3
   • PSI class III patients should be treated in an observation unit or with a short hospitalization 1
   • PSI classes IV-V patients should be treated as inpatients 1, 3
   • CURB-65 scores 0-1 indicate outpatient treatment, score 2 indicates possible hospitalization, and scores ≥3 indicate hospitalization 2
3. For ICU admission decisions:
   • Use the 2007 IDSA/ATS severe CAP criteria, which is more accurate than PSI or CURB-65 for predicting need for intensive care 1, 2

Limitations and Considerations

• PSI may underestimate severity in younger patients without comorbidities who develop severe respiratory failure, as age is heavily weighted in the scoring system 1, 3
• Clinical judgment should always accompany severity scores, as studies show physicians often admit low-risk patients for valid clinical reasons 4, 5
• Common reasons for admitting low-risk patients include comorbid illnesses (71.5%), concerning laboratory values or vital signs (29.3%), and recommendations from primary care or consulting physicians (19.3%) 4
• Hypoxia is a frequent factor (48%) contributing to admission of low-risk patients, suggesting clinical judgment appropriately supersedes the PSI in these cases 5

Outcomes and Benefits of Severity Assessment

• Using severity assessment tools in conjunction with clinical judgment improves patient outcomes compared to clinical judgment alone 2
• Systematic use of objective severity-of-illness criteria aids site-of-care decisions and is emerging as a step forward in patient management 1
• The routine use of PSI has been associated with a larger proportion of low-risk patients (particularly PSI classes I and II) being safely treated as outpatients 6
• PSI has proven effective in reducing avoidable hospital admissions, length of hospital stay, and overall healthcare costs 1, 3

Comparative Performance

• There are no significant differences in overall test performance between PSI, CURB-65, and CRB-65 for predicting mortality from CAP 7
• In identifying low-risk patients, PSI (groups I and II) has the best negative likelihood ratio 0.08 compared with CURB-65 (score 0-1) 0.21 and CRB-65 (score 0) 0.15 7
• For ICU admission decisions, the PSI and CURB-65 were not designed to help select the level of care needed by hospitalized patients 1

Special Considerations

• In elderly patients, CRB-65 is no longer predictive of low risk; instead, poor functional status is the best predictor of death 8
• Patients transferred to an ICU after admission to a hospital ward experience higher mortality than those directly admitted to the ICU from an emergency department, highlighting the importance of accurate initial severity assessment 1
• Assessment of oxygenation, unstable comorbidity, lactate levels, and biomarkers remain important considerations beyond scoring systems 8