Probiotics' effects on the incidence of nosocomial pneumonia in critically ill patients: a systematic review and meta-analysis Yi-Zhen Gong, the First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi, China 26 September 2012 To the Editor: We congratulate Liu et al. for their interesting report in a recent issue of the Critical Care, regarding the effects of probiotics on the incidence of nosocomial pneumonia in critically ill patients . There are some issues which need to be ad dressed in the article: Did only RCTs regarding the effects of probiotics be included this meta-analysis? What about those RCTs regarding the effects of synbiotics? If yes, why the trial conducted by Spindler-Vesel et al.  be included? If not, why this trial  did not be included? The authors should give a more detailed description of the inclusion/exclusion criteria in their report. References 1. Liu KX, Zhu YG, Zhang J, Tao LL, Lee JW, Wang XD, Qu JM: Probiotics' effects on the incidence of nosocomial pneumonia in critically ill patients: a systematic review and meta-analysis. Crit Care 2012, 16:R109. 2. Spindler-Vesel A, Bengmark S, Vovk I, Cerovic O, Kompan L: Synbiotics, prebiotics, glutamine, or peptide in early enteral nutrition: a randomized study in trauma patients. JPEN J Parenter Enteral Nutr 2007, 31:119-126. 3. Kotzampassi K, Giamarellos-Bourboulis EJ, Voudouris A, Kazamias P, Eleftheriadis E: Benefits of a synbiotic formula (Synbiotic 2000Forte) in critically Ill trauma patients: early results of a randomized controlled trial. World J Surg 2006, 30:1848-1855. Competing interests I have no conflicts of interest to disclose.