Statistical analysis
death, comorbidity, VAP, PA-VAP, pulmonary infections
RECURRENCE, EVENT, SENSITIVITY, PULMONARY INFECTIONS, REGRESSION
Baseline characteristics were reported according to the type of definitive antibiotic therapy (“definitive monotherapy”/“definitive combined therapy”), using frequencies and percentages for categorical data and using mean and standard deviation (sd) or median and interquartile range (IQR) for continuous data, according to their distribution and differences between groups were tested using Chi-squared or Fisher Exact test and Student t-test or Wilcoxon–Mann–Whitney test, respectively.The proportion of patients with definitive antimicrobial treatment based on combination of antibiotics was compared between “15-day” and the “8-day” groups of the iDIAPASON trial using a Chi-square test.The primary outcome was compared between groups using a Chi-square test. Time from appropriate antibiotic therapy to death in ICU or to censure at day 90 was represented using Kaplan–Meier survival curves and compared between groups using a Log-rank test. The proportion of patients with recurrent VAP in the ICU and the proportion of patients with MDR pathogens acquired during the ICU stay were compared between groups using a Chi-square test. The duration of mechanical ventilation and ICU length of stay were compared between groups using a Wilcoxon–Mann–Whitney test. The number of extra pulmonary infections was compared between groups using a Wilcoxon–Mann–Whitney test. The type of extra pulmonary infections was described.Sensitivity analyses were performed for all outcomes using model adjusted for randomization arm of the iDIAPASON study and SOFA score at inclusion. Logistic regression models were used for binary outcome, linear regression models for quantitative outcome after log-transformation, Cox proportional hazard model for survival time outcome and generalized linear model with negative-binomial distribution for count data (number of extra pulmonary infections). Considering ICU mortality and recurrence of VAP event, supplementary sensitivity analysis was made using propensity score (PS) approach. PS was built modeling the type of antibiotherapy using logistic regression model including age, gender, randomization arm of the original study, BMI and respiratory, cardiovascular, renal, neurological and hematological SOFA item as covariates. Hepatic SOFA item and the presence of at least one comorbidity at the admission were not included in the model, considering that they were associated with the type of antibiotic therapy administered (monotherapy or combination) but not with mortality nor recurrence of PA-VAP. The effect of type of antibiotic therapy on mortality on the one hand and on recurrence of PA-PAVM, on the other hand, was estimated using logistic regression models stratified on the quintiles of PS.All analyses were performed with the SAS software version 9·4 statistical software (SAS Institute Inc. Cary, NC, USA). All tests were two-sided and a P-value of less than 0.05 indicated statistical significance. No adjustment for multiple comparisons was made.