Human apolipoprotein CIII levels; evaluation of three assay methods.

Apolipoprotein CIII (apoCIII) is associated with triglyceride (TG)-rich particles like VLDL and exerts an inhibitory effect of lipoprotein lipase. Increased levels are related to cardiovascular diseases and diabetes and therefore apoCIII has been proposed as a useful biomarker. Even if several commercial assays for measuring apoCIII in human plasma/serum are available, data is scarce concerning their reliability and none is used clinically. In the present study a comparative investigation has been done. Two ELISA-based methods (Cusabio Biotech and Assay Pro) and one nephelometric assay (Siemens Healthcare) were investigated. Serum and plasma samples were obtained from healthy volunteers and from samples sent to the Laboratory of Clinical Chemistry, preferably with higher levels of TGs. The Cusabio Biotech assay did not yield any valid results. However, both the methods from Assay Pro and Siemens Healthcare showed good performance with similar dynamic ranges. The latter assay had lower CV and required less work. In healthy individuals, apoCIII levels were not affected by fasting, freezing or thawing, nor did we find any gender differences. Individuals with elevated levels of TG displayed higher apoCIII values. Females with oral intake of contraceptives had higher levels. In conclusion, the nephelometric assay showed the best performance with the lowest CV, was less labor intensive than an assay based on ELISA and could therefore be suitable for clinical use.