Influence of direct bilirubin and indirect bilirubin on the determination of high-density lipoprotein cholesterol polyanion with polymer/detergent method

Objective: To study the influence of direct bilirubin(DBIL) and indirect bilirubin(IBIL) on the determination result of serum high-density lipoprotein cholesterol(HDL-C) polyanion by polymer/detergent(PPD) method.Methods: The serum mixed with different levels of DBIL(5.0,17.5,40.5,70.0,102.0 μmol/L)and IBIL(5.0,17.0,40.0,71.5,104.0 μmol/L)was prepared and divided into high(2.54±0.22)mmol/L,middle(1.10±0.15)mmol/L and low(0.50±0.08)mmol/L groups according to the level of HDL-C.The level of DBIL and IBIL was determined by HITACHI 7170A automatic analyzer;the level of HDL-C of each serum specimen was determined by using both PPD method and phospho-wolframic acid magnesium precipitation(PTA-Mg²⁺) method.Results: The interference of DBIL was complicated,the serum specimen within normal DBIL level scope manifested fake advance in the determination result by the PPD method;when the level of DBIL exceeded 20.0 μmol/L,the determination result showed remarkably reduction;when the level of DBIL was 120.0 μmol/L,the HDL-C deviation was-46.29%,-36.89% and-22.73%,respectively in the high,middle and low groups of specimen.The interference of IBIL was not serious,when the level was 104.0 μmol/L,the deviation in each group was within5.0%.Conclusions: When the PPD method is used to determine HDL-C in clinical laboratory,the specimen should be diluted or treated with other experimental techniques to eliminate the interference if the level of DBIL is higher than 40.0 μmol/L.