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Reply to the Letter by Mengoli et al.

We would like to thank Mengoli et al 1 for their comments on our article suggesting survival benefits of fibrinogen concentrate in surgical patients. Mengoli et al criticized the inclusion of the REPLACE trial by Rahe-Meyer et al that was presented at international conferences in 2015 and published in the British Journal of Anaesthesia in 2016 and that probably represents the highest quality randomized trial ever published on the topic. When Mengoli et al 1 repeated the analyses without this trial they found only a trend (p 1⁄4 0.06) on survival benefit, as was already clearly stated in our original manuscript. The inclusion of “grey literature” (eg, trials that have not yet reached the full publication status at the time of the search) is indeed a highly appreciated part of the meta-analytic process. For example, a survey of 534 responders assessing the attitudes toward the inclusion of unpublished data in a meta-analysis revealed support for the use of unpublished material among a majority of the systematic reviewers (85.3%) and journal editors (68.6%). Obviously, “grey literature” does not include a description of all the employed methodology; it usually is considered “at risk of biases” and removed when performing subanalyses. Notably, the REPLACE trial by Rahe-Meyer et al has been published; it is a high-quality, low-risk-of-bias trial and the “grey data” that we included in our meta-analysis perfectly corresponded to the results of the published study. Because the topic is very controversial, we would like to repeat again the conclusions of our published meta-analysis: “Large multicenter trials are warranted in the perioperative period to confirm the promising findings of fibrinogen on clinically relevant endpoints.” For the time being, the only hemostatic agent that has demonstrated documented efficacy and safety in the perioperative period is low-dose tranexamic acid, and future trials need to compare the additive effect of any hemostatic agent on top of lowdose tranexamic acid in terms of efficacy and safety through large, multicenter, randomized trials.