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)