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

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.

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.

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.

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).

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.