Comparison analysis of an indirect measurement of friedwal formula method and direct measurment of immunoseparation method on low-density lipoprotein cholesterol measurement

Kim, Gyu Won; Cho, Byung Dong; Lee, Hyung Seok; Jung, Seung Hyun; Oh, Kil Chan; Yoon, Jang Uk; Baek, Seung Hun; Ryu, Kyu Hyung; Rhim, Chong Yun; Cho, Hyoun Chan

Abstract

BACKGROUND: In 2001, the third report the National Cholesterol Education Program (NCEP) has concluded that LDL cholesterol levels should be a major goal for preventing coronary artery disease and atherosclerotic events. Those in the higher risk groups should then have lipoprotein analysis to determine LDL cholesterol levels. LDL cholesterol has traditionally been estimated by the Friedwald forrmula : LDL-C=total cholesterol-[high density lipoprotein cholesterol (HDL-C)+trigryceride/5]. However, when trigryceride level is >400 mg/dL, this formula is inaccurate. Therefore, We have compared the direct LDL cholesterol immunoseparation method with Friedwald formula from both normotriglyceridemic (triglyceride400 mg/dL).
METHODS
The direct LDL cholesterol immunoseparation method was performed on 53 sera with triglyceride levels 61 to 1,684 mg/dL (classified as400 mg/dL : 31). Total cholesterol was measured enzymatic colorimetry. HDL cholesterol was measured in the supernatant after precipitating LDL by HDL cholesterol precipitating reagent containing dextran sulfate and magnesium chloride for serum. Direct LDL cholesterol was measured by immunoseparation method (Sigma Diagnostics, St Louis, Mo) that is based on selective absorption of HDL cholesterol and VLDL cholesterol by polystylene beads coated with goat polyclonal antibodies to human apolipoproteins. The cholesterol was measured by an enzamatic method on Hitachi 747. The linear regression and paird t-test were performed to evaluate the differences of data from Immunoseparation method and Friedwald formula.
RESULTS
In triglyceride400 mg/dL, the LDL cholesterol value obtained by the direct LDL-C assay on the 31 frozen sera studied was significantly different from that of Friedwald formula (103+/-38.4; 50.4+/-56.2 mg/dL). Therefore, Friedwald formula is unreliable in triglyceride>400 mg/dL.
CONCLUSION
Guidelines for treatment decisions, including diet and drug initiation, and therapeutic goals for high risk groups are based entirely on the LDL cholesterol level. At triglyceride levels >400 mg/dL, Friedwald fomula is inaccurate. Immunoseparation method is more rapid, higher specific, precise and helps monitor LDL lowering drugs and diets in triglyceride level>400 mg/dL.