Performance and Comparison of Assessment Models to Predict 30-Day Mortality in HAP Patients

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Performance and Comparison of Assessment Models to Predict 30-Day Mortality in Patients with Hospital-Acquired Pneumonia

Hospital-acquired pneumonia (HAP), including ventilator-associated pneumonia (VAP), is the most frequent nosocomial infection in China and is associated with significant morbidity and mortality. Despite advancements in antimicrobial therapies, mortality rates remain high, necessitating accurate risk stratification to guide clinical decision-making. Current guidelines recommend risk-based antibiotic regimens but lack precise tools for mortality prediction in HAP patients. This study evaluated five established scoring systems—pneumonia severity index (PSI), CURB-65 (consciousness, urea nitrogen, respiratory rate, blood pressure, and age ≥65 years), Acute Physiology and Chronic Health Evaluation II (APACHE II), Sequential Organ Failure Assessment (SOFA), and Quick Sequential Organ Failure Assessment (qSOFA)—to determine their utility in predicting 30-day mortality in non-surgical HAP patients.

Background and Rationale

HAP occurs 48 hours after hospitalization and is diagnosed via radiographic infiltrates with clinical features such as fever, leukocytosis/leukopenia, and purulent secretions. In China, HAP mortality remains substantial, with a reported 30-day mortality rate of 22.3% in prior epidemiological studies. Current guidelines emphasize risk stratification for antibiotic selection but rely on broad criteria like mechanical ventilation or septic shock, which may not capture early disease severity or atypical presentations. The 2018 Chinese Thoracic Society guidelines highlighted the need for validated assessment tools tailored to HAP patients, particularly those outside intensive care units (ICUs).

This study aimed to address this gap by evaluating existing scoring systems originally designed for sepsis, ICU patients, or community-acquired pneumonia (CAP). For instance, PSI and CURB-65 are CAP-specific tools, while APACHE II and SOFA assess organ dysfunction in critically ill patients. The qSOFA score, a simplified sepsis screening tool, was also included due to its feasibility for rapid bedside assessment.

Methodology

Study Design and Population

This retrospective, single-center study included 223 HAP patients from non-surgical departments at Peking University Third Hospital between 2012 and 2017. Exclusion criteria included age <18 years, perinatal status, coexisting extrapulmonary infections, and incomplete data. HAP diagnosis required radiographic evidence of infiltrates plus ≥2 clinical criteria. Patients were stratified into survivors and non-survivors based on 30-day outcomes.

Data Collection and Scoring Systems

Demographic data, comorbidities, and laboratory values within 24 hours of HAP diagnosis were collected. Scores were calculated using the worst values for each parameter:

  • PSI: Incorporates demographics, comorbidities, physical findings, and laboratory results.
  • CURB-65: Evaluates consciousness, urea >7 mmol/L, respiratory rate ≥30/min, systolic blood pressure <90 mmHg or diastolic ≤60 mmHg, and age ≥65 years.
  • APACHE II: Assesses acute physiology (12 variables), age, and chronic health status.
  • SOFA: Scores respiratory, cardiovascular, hepatic, coagulation, renal, and neurological systems.
  • qSOFA: Includes altered mentation, systolic blood pressure ≤100 mmHg, and respiratory rate ≥22/min.

Statistical Analysis

Nonparametric tests compared survivors and non-survivors. Receiver operating characteristic (ROC) curves determined discriminatory power via area under the curve (AUC). Delong’s test compared AUCs. Optimal cut-off values were derived using Youden’s index. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were reported.

Key Findings

Patient Characteristics

The cohort had a median age of 75 years (IQR: 63–84), with 70% males. Non-survivors (18.4%, 41/223) were older (79 vs. 73.5 years, P=0.036) and had higher rates of neoplastic (39% vs. 17%, P=0.002), cardiovascular (56.1% vs. 21.4%, P<0.001), and renal diseases (39% vs. 20.9%, P=0.014).

Score Performance

All scores were significantly higher in non-survivors (P<0.001):

  • PSI: 141 (non-survivors) vs. 99 (survivors).
  • CURB-65: 3 vs. 2.
  • SOFA: 6 vs. 2.
  • APACHE II: 21 vs. 11.
  • qSOFA: 1 vs. 0.

Mortality Stratification

Mortality increased across risk strata for all scores (P<0.001):

  • PSI: 5.7% (low), 9.2% (intermediate), 50.9% (high).
  • CURB-65: 6.6% (low), 14.9% (intermediate), 38.5% (high).
  • APACHE II: 1.2% (low), 17.9% (intermediate), 65.6% (high).
  • SOFA: 1.3% (low) vs. 27.6% (high).
  • qSOFA: 13.5% (low) vs. 48.4% (high).

Discriminatory Power

ROC analysis revealed the following AUC values:

  • APACHE II: 0.863 (95% CI: 0.806–0.920).
  • SOFA: 0.856 (0.796–0.915).
  • PSI: 0.808 (0.728–0.889).
  • qSOFA: 0.767 (0.686–0.848).
  • CURB-65: 0.744 (0.660–0.827).

APACHE II and SOFA outperformed CURB-65 and qSOFA (Table 5):

  • APACHE II vs. CURB-65: Z=3.055, P=0.002.
  • APACHE II vs. qSOFA: Z=3.017, P=0.003.
  • SOFA vs. CURB-65: Z=2.589, P=0.010.
  • SOFA vs. qSOFA: Z=2.170, P=0.030.

Optimal Cut-Off Values

New thresholds maximized Youden’s index:

  • SOFA ≥4: Sensitivity 75.6%, specificity 78.0%, PPV 42.9%, NPV 92.8%.
  • APACHE II ≥14: Sensitivity 85.4%, specificity 70.3%, PPV 39.3%, NPV 95.5%.
  • qSOFA ≥1: Sensitivity 85.4%, specificity 58.8%, PPV 31.8%, NPV 94.7%.

Clinical Implications and Discussion

Superiority of APACHE II and SOFA

APACHE II and SOFA demonstrated the highest discriminatory power, likely due to their comprehensive assessment of organ dysfunction, a critical driver of HAP mortality. The SOFA score’s focus on multisystem failure aligns with sepsis pathophysiology, while APACHE II’s inclusion of chronic health conditions captures comorbidities prevalent in HAP patients. These tools are particularly valuable in non-surgical wards, where patients often have complex medical histories.

Role of qSOFA

Although qSOFA had lower specificity, its simplicity makes it practical for rapid triage outside ICUs. A score ≥1 identified 85.4% of non-survivors, enabling early escalation of care. However, its low PPV (31.8%) risks overestimating severity, necessitating adjunctive testing.

Limitations of PSI and CURB-65

PSI and CURB-65, designed for CAP, showed moderate performance. Their reliance on demographics and limited organ dysfunction metrics reduces applicability to HAP, where comorbidities and prolonged hospitalization alter risk profiles.

Practical Considerations

The derived cut-offs enhance clinical utility:

  • APACHE II ≥14: Triggers intensive monitoring or empiric broad-spectrum antibiotics.
  • SOFA ≥4: Warrants ICU referral for multisupportive care.
  • qSOFA ≥1: Justifies prompt sepsis evaluation and laboratory testing.

Study Limitations

Retrospective design and single-center data limit generalizability. Exclusion of VAP patients and small sample size may underrepresent heterogeneity. Prospective multicenter studies are needed to validate thresholds and refine models for HAP-specific mortality prediction.

Conclusions

APACHE II and SOFA scores calculated within 24 hours of HAP diagnosis effectively predict 30-day mortality in non-surgical patients, with AUCs >0.85. qSOFA serves as a rapid screening tool, albeit with lower specificity. Adoption of these scores could optimize risk stratification, guide antibiotic stewardship, and improve outcomes in HAP management. Future research should focus on developing HAP-specific models and validating findings across diverse populations.

doi.org/10.1097/CM9.0000000000001252

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