Predictive Performance of Risk Factors for MDR Pathogens in Nosocomial Pneumonia

Rationale: In 2017 the International ERS/ESICM/ESCMID/ALAT (European) guidelines defined new risk factors for multidrug resistant (MDR) pathogens in patients with nosocomial pneumonia. Objective: To assess the predictive performance of these newly defined risk factors for MDR pathogens. Methods: We enrolled 507 adult patients with nosocomial pneumonia, treated in 6 intensive care units at the Hospital Clinic of Barcelona, Spain. Of the 503 patients at high MDR and mortality risk, 275 (54%) had no septic shock and 228 (46%) had septic shock. Results: Admission to hospital settings with high rates of MDR pathogens (n = 421, 83%) and prior antibiotic use (n = 399, 79%) showed the highest prevalence in the overall population, with a sensitivity of 92% and 85% and a negative predictive value of 85% and 82%, respectively. However, low specificities and low positive predictive values were found. Previous respiratory MDR pathogen isolation was less common (n = 17, 3%), but presented a specificity and positive predictive value (PPV) of 100%. The AUC ROC were lower than 0.6 for all risk factors and combinations. Conclusions: The risk factors proposed by ERS/ESICM/ESCMID/ALAT showed low accuracy for predicting MDR pathogens in ICU-AP. Admission to hospital settings with high rates of MDR pathogens and prior antibiotic use were the most prevalent risk factors, with a high sensitivity for predicting these microorganisms; prior positive cultures for MDR pathogens showed high specificity but very low sensitivity. Nor did combinations of risk factors show any great accuracy for predicting these microorganisms. Further studies assessing combined strategies of risk stratification and complementary methods are now warranted.