Korean J Clin Pathol.  1997 Dec;17(6):993-1001.

Direct Measurement of Low-Density Lipoprotein Cholesterol with Immunoseparation Method

• Hong KS

Abstract

BACKGROUND: Most of clinical laboratories currently estimate low-density lipoprotein cholesterol (LDL-C) using the Friedewald equation (FLDL-C) , which requires fasting specimens and is inaccurate with increasing triglyceride (TG) levels. The author evaluated a new assay which directly measures LDL-C (DLDL-C) using the direct LDL immunoseparation reagent and subsequent measurement of cholesterol by conventional method.
METHODS
Direct LDL-cholesterol assay (Sigma Diagnostics, St. Louis, MO) was analyzed in 110 fresh serum samples from fasting patients for physical examination at Ewha Womans University Tongdaemun Hospital. In FLDL-C, total cholesterol and TG were measured by enzymatic methods and HDL-C by direct method. Lp (a) , ape-A and apo-B were measured by nephelometry (Array 360, Bookman, USA). The paired t-test, Pearson product-moment correlation coefficients and linear regression were calculated by Microsoft Excel. Within-run precision and between-run precision were determined by two level reagent control sera containing normal and high concentration.
RESULTS
Precision studies were provided within and between-run CVs in the range of 2.9-5.8% and 6.5-12.1%, respectively. On the comparison of the bias between FLDL-C and DLDL-C, there was no significant difference between the two methods in 0.37-6.48 g/L 7G and the same in less than 4.0 and 2.0 g/L TG. But the results of DLDL-C were higher than FLDL-C (P(0.05) in 2.0-4.0 g/L TG. The correlation coefficient between the two was 0.7637 and Y(DLDL-C)= 0.87X(FLDL-C) + 0.16 at a TG range of 0.37-6.48 g/L. The concordance of low-density lipoprotein classification for DLDL-C compared to FLDL-G at the NCEP cut-point was 91.2% below 1.30 g/L, 73.3% at 1.30-1.59 g/L and 100% above 1.60 g/L FLDL-C. The LDL-C was highly correlated with total cholesterol and ape-B concentrations.
CONCLUSIONS
There was a high positive correlation between DLDL-C and FLDL-C below TG 4.0 g/L and direct determination is necessary above 2.0 g/L of TG and will require proper calibrators in measuring the DLDL-C.

MeSH Terms

Apolipoproteins B
Bias (Epidemiology)
Cholesterol*
Classification
Fasting
Female
Humans
Linear Models
Lipoproteins*
Nephelometry and Turbidimetry
Physical Examination
Triglycerides
Apolipoproteins B
Cholesterol
Lipoproteins