Acknowledgements
The authors would like to thank Dr. A. Saul for English translation of the manuscript and Mr. A. Legrand (investigation project manager DRCI CHU Nantes), Mr. B. Orofiamma (Atlanstat) for their assistance in methodology and statistics and Dr. M. Royer for the coordination between the two centers (Groupe ELSAN, 58 bis rue de la Boétie 75008 Paris).