Method of quantifying small-sized low density lipoprotein
A fast and simple method for fractional measurement of a small particle LDL entails separating the small particle LDL and HDL from other lipoproteins, and then measuring cholesterol, triglycerides, or proteins in the separated small particle LDL.
1. A method for quantifying small particle LDL in a test sample, comprising:
(i) removing lipoproteins other than small particle LDL and HDL from said test sample by adding a separation agent comprising a polyanion, a divalent cation, and a monovalent cation, wherein the monovalent cation is at a final concentration of 50 mmol/L or less; then
(ii) eliminating HDL by treating the test sample with cholesterol esterase and cholesterol oxidase in the presence of a surface active agent that is polyalkylene oxide; and
(iii) quantifying small particle LDL in the test sample from step (ii) by measuring the amount of LDL.
2. A method according to claim 1 , wherein the polyanion is selected from the group consisting of heparin, phosphotungstic acid and dextran sulfate.
3. A method according to claim 2 , wherein, when the polyanion is added to the test sample, the final concentration of the polyanion is 10-250 U/mL for heparin, 0.02-1.25% for dextran sulfate and 0.02-1.25% for phosphotungstic acid.
4. A method according to claim 1 , wherein the divalent cation is selected from the group consisting of Mn 2+ , Mg 2+ and Ca 2+ .
5. A method according to claim 4 , wherein, when the divalent cation is added to the test sample, the final concentration of the divalent cation is 2.5-35 mmol/L for Mn 2+ , 2.5-125 mmol/L for Mg 2+ and 1-75 mmol/L for Ca 2+ .
6. A method according to claim 1 , wherein the monovalent cation is selected from the group consisting of Na + , K + and Li + .
7. A method according to claim 1 , wherein measuring the amount of LDL is carried out by using a reagent which is used for selectively measuring cholesterol in LDL and which does not require fractionation.
8. A method according to claim 1 , wherein measuring the amount of LDL is carried out by using a reagent which is used for selectively measuring triglycerides in LDL and which does not require fractionation.
9. A method according to claim 1 , wherein measuring the amount of LDL is carried out by using an anti-human apoprotein B antibody.
10. A method according to claim 1 , wherein the surface active agent is selected from the group consisting of polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene octylphenyl ether and polyoxyethylene nonylpheny ether.
11. A method for quantifying small particle LDL in a test sample, comprising:
(i) removing lipoproteins other than small particle LDL and HDL from said test sample, by adding a separation agent consisting of polyethylene glycol;
(ii) eliminating HDL by treating the test sample from step (i) with cholesterol esterase and cholesterol oxidase in the presence of a surface active agent, wherein the surface active agent is polyalkylene oxide; and
(iii) quantifying small particle LDL in the test sample from step (ii) by measuring the amount of LDL.
12. A method according to claim 11 wherein the final concentration of polyethylene glycol is 2-5% by weight when polyethylene glycol is added to the test sample.
13. A method according to claim 11 , wherein the surface active agent is selected from the group consisting of polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene octylphenyl ether and polyoxyethylene nonylpheny ether.
14. A method for separating small particle LDL from a test sample that contains LDLs, comprising precipitating LDLs other than small particle LDL by adding a separation agent comprising a monovalent cation at a final concentration of 50 mmol/L or less to the test sample.
15. A method according to claim 14 , wherein said separation agent further comprises a polyanion and a divalent cation.
16. A method according to claim 15 , wherein the polyanion is selected from the group consisting of heparin, phosphotungstic acid and dextran sulfate.
17. A method according to claim 16 , wherein, when the polyanion is added to the test sample, the final concentration of the polyanion is 10-250 U/mL for heparin, 0.02-1.25% for dextran sulfate and 0.02-1.25% for phosphotungstic acid.
18. A method according to claim 15 , wherein the divalent cation is selected from the group consisting of Mn 2+ , Mg 2+ and Ca 2+ .
19. A method according to claim 18 , wherein, when the divalent cation is added to the test sample, the final concentration of the divalent cation is 2.5-35 mmol/L for Mn 2+ , 2.5-125 mmol/L for Mg 2+ and 1-75 mmol/L for Ca 2+ .
20. A method according to claim 14 , wherein the monovalent cation is selected from the group consisting of Na + , K + and Li + .