A prospective randomized double-blinded trial. Study protocol Abbreviated Version Jan 25 2012 Corresponding author: Pall T. Onundarson, M.D., Department of Laboratory Hematology and Hemostasis Center, K-building, Landspitali Hringbraut, 101 Reykjavik, Iceland, Phone: +354 543 1000/5010, Fax +354 543 5539, email: pallt@landspitali.is.