QUANTIFICATION OF APOLIPOPROTEIN A-IV IN HUMAN PLASMA BY IMMUNONEPHELOMETRY

We developed a nephelometric procedure for determining concentrations of human plasma apolipoprotein (ape) A-IV. Results obtained correlate well with those measured by an established electroimmunodiffusion assa y (r = 0.98; n = 56). Intra- and interassay CVs were 2.4% and 2.0%, re spectively, indicating excellent precision and reproducibility. Variou s conditions of sample treatment, such as adequate storage, freezing, and thawing, did not affect results significantly. However, keeping sa mples at room temperature for 4 days led to a slight increase in measu red values. Preincubation with a cholesterinesterase-detergent mixture abolished interference from triglyceride-rich lipoproteins, allowing assay of samples containing triglycerides as great as 10 g/L. The assa y is easily applicable to clinical laboratories for routine diagnostic use, as shown with hypertriglyceridemic plasmas and samples with a br oad range of apo A-IV concentrations.