Do Optimal Prognostic Thresholds in Continuous Physiological Variables Really Exist? Analysis of Origin of Apparent Thresholds, with Systematic Review for Peak Oxygen Consumption, Ejection Fraction and BNP - Giannoni,A; Baruah,R; Leong,T; Rehman,MB; Pastormerlo,LE; Harrell,FE; Coats,AJS; Francis,DP (PLOS ONE, 2014)