Method for measuring cholesterol in low-density lipoprotein, measurement reagent, and measurement kit

1. A method for measuring cholesterol in low-density lipoprotein in a sample, the method comprising:

mixing the sample and an aqueous solvent which comprises:

(i) a combination of cholesterol ester hydrolase and cholesterol oxidase or (ii) a combination of cholesterol ester hydrolase, an oxidized coenzyme and cholesterol dehydrogenase,

one or more surfactants selected from the group consisting of a polyoxyethylene alkyl ether and a polyoxyethylene polyoxypropylene alkyl ether,

a polyoxyethylene polyoxypropylene copolymer and

a polyoxypropylene derivative not comprising any polyoxyethylene in a molecule, to react cholesterol in low-density lipoprotein in the sample with (i) the combination of cholesterol ester hydrolase and cholesterol oxidase or (ii) the combination of cholesterol ester hydrolase, an oxidized coenzyme and cholesterol dehydrogenase; and

measuring a substance formed or consumed in the reaction from the low-density lipoprotein,

with the proviso that the aqueous solvent does not comprise any surfactant having an alkylphenol structure.

2. The method according to claim 1 , wherein the alkyl in the polyoxyethylene alkyl ether and the polyoxyethylene polyoxypropylene alkyl ether is independently an alkyl having 8 to 20 carbon atoms.

3. The method according to claim 1 , wherein the polyoxypropylene derivative is a polypropylene glycol or a polyoxypropylene glyceryl ether.

4. The method according to claim 1 , wherein the substance formed is a hydrogen peroxide.

5. The method according to claim 4 , wherein the hydrogen peroxide is measured using a reagent for measuring hydrogen peroxide.

6. The method according to claim 1 , wherein the substance formed is a reduced coenzyme.

7. The method according to claim 6 , wherein the reduced coenzyme is measured using a reagent for measuring a reduced coenzyme.

8. The method according to claim 1 , wherein the aqueous solvent comprises the cholesterol ester hydrolase and the cholesterol oxidase.

9. The method according to claim 8 , wherein the cholesterol ester hydrolase and the cholesterol oxidase are reacted with the sample, thereby forming hydrogen peroxide.

10. The method according to claim 8 , wherein alkyl in the polyoxyethylene alkyl ether and the polyoxyethylene polyoxypropylene alkyl ether is independently an alkyl having 8 to 20 carbon atoms.

11. The method according to claim 8 , wherein the polyoxypropylene derivative comprises a polypropylene glycol or a polyoxypropylene glyceryl ether.

12. The method according to claim 1 , wherein the aqueous solvent excludes polyoxyethylene alkyl ether.

13. The method according to claim 1 , wherein the aqueous solvent comprises the polyoxyethylene polyoxypropylene alkyl ether.

14. The method according to claim 1 , wherein the method excludes any removal of cholesterol in lipoprotein other than the low-density lipoprotein in a sample before measurement of the low-density lipoprotein-cholesterol.

15. The method according to claim 1 , wherein the sample comprises at least one selected from the group consisting of whole blood, plasma, and serum.

16. A method for measuring cholesterol in total low-density lipoprotein in a sample, the method comprising:

mixing the sample and an aqueous solvent which comprises:

(i) a combination of cholesterol ester hydrolase and cholesterol oxidase or (ii) a combination of cholesterol ester hydrolase, an oxidized coenzyme and cholesterol dehydrogenase,

one or more surfactants selected from the group consisting of a polyoxyethylene alkyl ether and a polyoxyethylene polyoxypropylene alkyl ether,

a polyoxyethylene polyoxypropylene copolymer and

a polyoxypropylene derivative not comprising any polyoxyethylene in a molecule, to react cholesterol in low-density lipoprotein in the sample with (i) the combination of cholesterol ester hydrolase and cholesterol oxidase or (ii) the combination of cholesterol ester hydrolase, an oxidized coenzyme and cholesterol dehydrogenase; and

measuring a substance formed or consumed in the reaction,

with the proviso that the aqueous solvent does not comprise any surfactant having an alkylphenol structure.

17. The method according to claim 16 , wherein

the substance formed or consumed in the reaction is measured from the low-density lipoprotein, and

the method excludes any removal of cholesterol in lipoprotein other than low-density lipoprotein in a sample before measurement of low-density lipoprotein-cholesterol.

18. A method for measuring cholesterol in low-density lipoprotein in a sample, the method comprising:

mixing the sample and an aqueous solvent which comprises:

(i) a combination of cholesterol ester hydrolase and cholesterol oxidase or (ii) a combination of cholesterol ester hydrolase, an oxidized coenzyme and cholesterol dehydrogenase,

one or more surfactants selected from the group consisting of a polyoxyethylene alkyl ether and a polyoxyethylene polyoxypropylene alkyl ether,

a polyoxyethylene polyoxypropylene copolymer and

a polyoxypropylene derivative not comprising any polyoxyethylene in a molecule, to react cholesterol in low-density lipoprotein in the sample with (i) the combination of cholesterol ester hydrolase and cholesterol oxidase or (ii) the combination of cholesterol ester hydrolase, an oxidized coenzyme and cholesterol dehydrogenase; and

measuring a substance formed or consumed in the reaction,

with the proviso that the aqueous solvent does not comprise any surfactant having an alkylphenol structure,

wherein the method excludes any removal of cholesterol in lipoprotein other than the low-density lipoprotein in a sample before measurement of the low-density lipoprotein-cholesterol.