Method of multiquantification for cholesterol of low-density lipoprotein
Provided is a method of stabilizing a reagent that allows simultaneous quantification of LDL cholesterol and total cholesterol by a single measurement by suppressing spontaneous color development thereof. A method of quantification for cholesterol in low density lipoprotein and total cholesterol in a biological sample by the single measurement comprises a first step of treating lipoproteins other than low density lipoprotein in the biological sample to generate hydrogen peroxide and a second step of converting the hydrogen peroxide obtained in the first step to a quinone dye and treating remaining low density lipoprotein and converting generated hydrogen peroxide to the quinone dye, where the quinone dye is not formed in the first step, and cholesterol in low density lipoprotein and total cholesterol are quantified from the amount of the quinone dye formed in the second step by the single measurement.
1. A method of quantification for cholesterol in low density lipoprotein and total cholesterol simultaneously in a biological sample, comprising:
(i) adding a first reagent in the biological sample such that hydrogen peroxide is generated from lipoproteins other than low density lipoprotein; and
(ii) adding a second reagent to the biological sample of step (i) such that the hydrogen peroxide generated in step (i) is converted to a quinone dye and that additional hydrogen peroxide is generated from low density lipoprotein and converted to the quinone dye,
wherein the quantity of cholesterol in low density lipoprotein and the quantity of total cholesterol are determined by readings of absorbance at different time points following addition of the second reagent.
2. The method of claim 1 , wherein:
(a) said first reagent comprises a surfactant that acts on lipoproteins other than low density lipoprotein, a cholesterol esterase, a cholesterol oxidase and a compound that is either 4-aminoantipyrine or a phenolic or anilinic hydrogen donor compound;
(b) said first reagent does not comprise peroxidase; and
(c) said second reagent comprises a surfactant that acts on low density lipoprotein, a cholesterol esterase, a cholesterol oxidase, peroxidase and a compound that is either 4-aminoantipyrine or a phenolic or anilinic hydrogen donor compound but different from the compound in the said first reagent.
3. The method of claim 1 , wherein the first reading of absorbance is taken at 30 seconds after addition of said second reagent, and the second reading of absorbance is taken at 5 minutes after addition of said second reagent.
4. The method of claim 1 , wherein the measurement is performed by an automatic analyzer for clinical chemistry testing.