Measurement of serum lipoproteins
Although a more accurate estimate of a person's risk of cardiovascular disease can be made on the basis of the number of lipoprotein particles per unit volume in the person's blood, current methods all rely on measuring the mass of lipoprotein cholesterol per unit volume. It has been discovered that a rapid and accurate lipoprotein particle count can be obtained by photometry. A method and apparatus are provided for measuring the number of lipoprotein particles in a sample using photometry.
1. A method of measuring lipoprotein particle concentration in a sample from a subject, the method comprising: (a) separating at least an HDL fraction, an LDL, fraction, and a VLDL fraction in a sample by centrifugation; (b) obtaining a measurement of the light scattering from the LDL fraction; (c) determining an apolipoprotein B concentration in the LDL fraction and (d) transforming the measurement of the light scattering from the LDL fraction to an LDL particle concentration.
2. The method of claim 1 , wherein the transforming of step (d) is accomplished according to an LDL specific algorithm.
3. The method of claim 2 further comprising separating at least an HDL fraction, a lipoprotein A (LpA) fraction an LDL fraction, an IDL fraction and a VLDL fraction in a sample.
4. The method of claim 3 , wherein the sample is contained in a tube and the tube is sampled from the bottom so as to collect the fractions in descending order of density.
5. The method of claim 1 , wherein the sample is contained in a tube and the tube is sampled from the bottom so as to collect the fractions in descending order of density.
6. The method of claim 1 , further comprising: (d) obtaining a measurement of the light scattering from the HDL fraction; and (e) obtaining a measurement of the light scattering from the VLDL fraction; wherein the steps of obtaining measurements of the light scattering of the HDL, LDL, and VLDL fractions are performed in order of descending density.
7. The method of claim 1 , wherein the sample is a blood sample, further comprising separating at least an HDL fraction, a lipoprotein A (LpA) fraction, an LDL fraction, an IDL fraction, and a VLDL fraction in the sample; and transporting each fraction to a light scattering counter in order of descending density.
8. A method of measuring lipoprotein particle concentration in a sample from a subject, the method comprising: (a) separating at least an HDL fraction, an LDL, fraction, and a VLDL fraction in a sample using centrifugation; (b) obtaining a measurement of the light scattering from the LDL fraction; and (c) transforming the measurement of the light scattering from the LDL fraction to an LDL particle concentration using an LDL specific algorithm, wherein the algorithm is y=1.764×10 −3 mg+(8.52×10 −4 mg V −1 min −1 )x, where y is the mass of apolipoprotein B in mg and x is the LDL peak area in V(min).
9. The method of claim 2 , wherein the LDL specific algorithm is y=1.764×10 −3 mg+(8.52×10 −4 mg V −1 min −1 )x, where y is the mass of apolipoprotein B in mg and x is the LDL peak area in V(min).