Risk stratification and prognostic performance of the predisposition, infection, response, and organ dysfunction (PIRO) scoring system in septic patients in the emergency department: a cohort study

Abstract

Introduction: The predisposition, infection, response and organ dysfunction (PIRO) staging system was designed as a stratification tool to deal with the inherent heterogeneity of septic patients. The present study was conducted to assess the performance of PIRO in predicting multiple organ dysfunction (MOD), intensive care unit (ICU) admission, and 28-day mortality in septic patients in the emergency department (ED), and to compare this scoring system with the Mortality in Emergency Department Sepsis (MEDS) and Acute Physiology and Chronic Health Evaluation (APACHE II) scores.

Methods: Consecutive septic patients (n = 680) admitted to the ED of Beijing Chao-Yang Hospital were enrolled. PIRO, MEDS, and APACHE II scores were calculated for each patient on ED arrival. Organ function was reassessed within 3 days of enrollment. All patients were followed up for 28 days. Outcome criteria were the development of MOD within 3 days, ICU admission or death within 28 days after enrollment. The predictive ability of the four components of PIRO was analyzed separately. Receiver operating characteristic (ROC) curve and logistic regression analysis were used to assess the prognostic and risk stratification value of the scoring systems.

Results: Organ dysfunction independently predicted ICU admission, MOD, and 28-day mortality, with areas under the ROC curve (AUC) of 0.888, 0.851, and 0.816, respectively. The predictive value of predisposition, infection, and response was weaker than that of organ dysfunction. A negative correlation was found between the response component and MOD, as well as mortality. PIRO, MEDS, and APACHE II scores significantly differed between patients who did and did not meet the outcome criteria (P < 0.001). PIRO and APACHE II independently predicted ICU admission and MOD, but MEDS did not. All three systems were independent predictors of 28-day mortality with similar AUC values. The AUC of PIRO was 0.889 for ICU admission, 0.817 for MOD, and 0.744 for 28-day mortality. The AUCs of PIRO were significantly greater than those of APACHE II and MEDS (P < 0.05) in predicting ICU admission and MOD.

Conclusions: The study indicates that PIRO is helpful for risk stratification and prognostic determinations in septic patients in the ED.

Figure 1

Receiver operating characteristic curves of the PIRO, MEDS and APACHE II scores for predicting outcomes. (a) ICU admission. (b) Development of multiple organ dysfunction. (c) Twenty-eight-day mortality. APACHE, Acute Physiology and Chronic Health Evaluation; MEDS, Mortality in Emergency Department Sepsis; PIRO, predisposition (P), infection (I), response (R), and organ dysfunction (O).

Figure 2

Mean scores of severity systems between patients who did and did not meet the outcome criteria. (a) Acute Physiology and Chronic Health Evaluation (APACHE) II score. (b) Mortality in Emergency Department Sepsis (MEDS) score. (c) Predisposition, infection, response, and organ dysfunction (PIRO) score. No, patients did not meet the outcome criteria; yes, patients met the outcome criteria. MOD, multiple organ dysfunction.