Thrombocytopenia in medical-surgical critically ill patients: prevalence, incidence, and risk factors. - Crowther,M.A.; Cook,D.J.; Meade,M.O.; Griffith,L.E.; Guyatt,G.H.; Arnold,D.M.; Rabbat,C.G.; Geerts,W.H.; Warkentin,T.E. (J Crit Care, 2005)