Comparative Study for the measurement of HDL Cholesterol between a direct Assay and a Precipitation Method

Background: The semiautomatic devices used in conventional laboratories rely on the precipitation method in measuring HDL-C concentrations, while the automated devices often used in hospitals and modern chemical laboratories use the direct method. It is of a particular importance for the clinical laboratory to provide accurate, reliable, and easy –to- perform measurement of HDL-C, especially at the decision points of 35 and 60 mg/dl. A significant problem with HDL precipitation methods is the interference from elevated triglyceride levels. Objectives: To know if the results of precipitation method in measuring HDL-C concentrations, match the results of the direct method, we compared the precipitation method with the direct assay according to the difference in triglyceride levels. Design and methods: 211 serum samples were collected from patients who has fasted overnight. HDL-C levels measured by the routine dextran sulfate-Mg2+ precipitation compared with the direct assay as a reference method. Results: HDL-C precipitation method interferences with triglyceride levels more than 300 mg/dl. The strongest correlation between direct HDL-C and sedimentary HDL-C was found when the level of TG concentration was less than 100mg/dl (P value = 0.0001, r = o.81), and the weakest relationship was found when the concentration of TG was greater than 300mg/dl (P value = 0.0417, r = 0.47). The coefficient of variation in the values of sedimentary HDL-C was high when the values of TG greater than 300mg/dl (CV =0.47). Conclusions: The results of the HDL-C values obtained in the precipitation method adopted by the semiautomatic devices comparable to the results of HDL-C values obtained directly by the automated devices when the concentration of triglycerides less than 300 mg/dl.