The nonlinearity seen for LDL-cholesterol with lyophilized material is a matrix effect.
Kroll
M H
MH
Chesler
R
R
D008078:Cholesterol, LDL / Q000097:blood*; D005612:Freeze Drying; D006801:Humans; D016014:Linear Models; D011933:Reagent Kits, Diagnostic
D008078:Cholesterol, LDL; D011933:Reagent Kits, Diagnostic