Method of quantitatively measuring small particle low density lipoproteins
The present invention provides a fast and simple method for fractional measurement of small particle low density lipoprotein (LDL). The method for quantifying small particle LDL in a test sample entails a first step of separating the small particle LDL from other low density lipoproteins, and a second step of measuring cholesterol, triglycerides or proteins in the separated small particle LDL.
1. A method for quantifying a small particle low density lipoprotein in a test sample, comprising a first step for separating the small particle low density lipoprotein from other low density lipoproteins, and a second step for measuring cholesterol, triglycerides or proteins in the separated small particle low density lipoprotein, wherein a separation agent comprising polyanion and 90-150 mmol/L of divalent cation is used to separate the small particle low density lipoprotein from other low density lipoproteins in the first step, and wherein the separation agent does not contain monovalent cation.
2. The method according to claim 1 , wherein the polyanion used in said first step is selected from the group consisting of heparin, phosphotungstic acid and dextran sulfate.
3. The 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. The method according to claim 1 , wherein the divalent cation used in said first step is selected from the group consisting of Mn 2+ , Mg 2+ and Ca 2+ .
5. The 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. The method according to claim 1 , wherein the measurement of cholesterol in said second step is carried out by using a reagent which is used for quantitatively measuring cholesterol in a low density lipoprotein and which does not require fractionation.
7. The method according to claim 1 , wherein the measurement of triglycerides in said second step is carried out by using a reagent which is used for quantitatively measuring triglycerides in a low density lipoprotein and which does not require fractionation.
8. The method according to claim 1 , wherein the measurement of protein in said second step is carried out by using an anti-human apoprotein B antibody.
9. A method for separating a small particle low density lipoprotein from a test sample comprising a step in which low density lipoproteins other than the small particle low density lipoprotein are precipitated by adding a separation agent comprising a polyanion and 90-150 mmol/L of a divalent cation to the test sample, wherein the separation agent does not contain monovalent cation.
10. The method for separating a small particle low density lipoprotein according to claim 9 , wherein the polyanion is selected from the group consisting of heparin, phosphotungstic acid and dextran sulfate.
11. The method for separating a small particle low density lipoprotein according to claim 10 , 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.
12. The method for separating a small particle low density lipoprotein according to claim 9 , wherein the divalent cation is selected from the group consisting of Mn 2+ , Mg 2+ , and Ca 2+ and 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+ .