PIRO score for community-acquired pneumonia: A new prediction rule for assessment of severity in intensive care unit patients with community-acquired pneumonia*

OBJECTIVE: To develop a severity assessment tool to predict mortality in community-acquired pneumonia (CAP) patients in intensive care unit (ICU), comparing its performance with Acute Physiology and Chronic Health Evaluation (APACHE) II score and American Thoracic Society/Infectious Disease Society of America (ATS/IDSA) criteria as a prognostic index in CAP patients requiring ICU admission. DESIGN: Secondary analysis of prospective observational cohort study. SETTING: Thirty-three ICUs. PATIENTS: Five hundred and twenty-nine adult patients with CAP requiring ICU admission. MEASUREMENTS AND MAIN RESULTS: A severity assessment score was developed based on the PIRO (predisposition, insult, response, and organ dysfunction) concept including the presence of the following variables: Comorbidities (chronic obstructive pulmonary disease, immunocompromise); age >70 years; multilobar opacities in chest radiograph; shock, severe hypoxemia; acute renal failure; bacteremia and acute respiratory distress syndrome. PIRO score was obtained at ICU within 24 hours from admission, and one point was given for each present feature (range, 0-8 points). The mean PIRO score was significantly higher in nonsurvivors than in survivors (4.6 +/- 1.2 vs. 2.3 +/- 1.4). Considering the observed mortality for each PIRO score, the patients were stratified in four levels of risk: a) Low, 0-2 points; b) Mild, 3 points; c) high, 4 points; and d) Very high, 5-8 points. Mild-risk (hazard ratio [HR] 1.8; 95% confidence interval [CI] 1.1-2.9; p < 0.05), high-risk (HR 3.1; 95% CI = 2.0-4.7; p < 0.001), and very high risk levels (HR 6.3; 95% CI = 4.2-9.4; p < 0.001) were significantly associated with higher risk of death in Cox proportional hazards regression analysis. Furthermore, analysis of variance showed that higher levels of PIRO score were significantly associated with higher mortality (p < 0.001), prolonged length of stay in the ICU (p < 0.001), and days of mechanical ventilation (p < 0.001). Receiver operating characteristic curves showed that PIRO score (area under the curve [AUC] = 0.88) performed better than APACHE II (AUC = 0.75, p < 0.001) and ATS/IDSA criteria (AUC = 0.80, p < 0.001) to predict 28-day mortality. CONCLUSIONS: The PIRO score performed well as 28-day mortality prediction tool in CAP patients requiring ICU admission with a better performance than APACHE II and ATS/IDSA criteria in this subset of patients. Furthermore, PIRO score also is associated with increased healthcare resource utilization in CAP patients admitted in the ICU.