Immunoturbidimetric method for routine determinations of apolipoproteins A-I, A-II, and B in normo- and hyperlipemic sera compared with immunonephelometry.

Abstract

We describe a method for routine immunoturbidimetry of apolipoproteins (apo) A-I, A-II, and B in both normo- and hyperlipemic sera. A special antiserum reagent, consisting of a highly concentrated mixture of nonionic and anionic detergents (final concentration in the assay, 36 g/L), rapidly removes intrinsic turbidities of even strongly lipemic sera without interfering with the antigen-antibody precipitation reaction. The method has good precision, and obviates the need for special sample pretreatment, extended incubation periods, and measurment of sample blanks. A comparison with established immunoephelometric assays generally showed close agreement for analytical recoveries of the three apolipoproteins. However, in samples containing greater than or equal to 18 g of triglycerides per liter, the nephelometric assays yielded about two- to threefold higher values for apo A-II and B than did the turbidimetric procedure. To elucidate this discrepancy, we used the turbidimetric methods to assay sera with and without enzymatic lipolytic pretreatment. Even for samples with triglyceride concentrations up to 60 g/L, complete enzymatic lipolysis (as evidenced by thin-layer chromatography) did not significantly alter the recoveries of apo A-II and B from those obtained with the untreated specimens. Thus the immunoturbidimetric methods yield reliable results for apo A-I, A-II, and B, not only in normo- but also in hyperlipemic sera.

Apolipoprotein A‐I as a candidate serum marker for the response to lithium treatment in bipolar disorder

“…In this method, human apo A‐I binds specifically to a precipitating antibody (sheep anti‐apo A‐I diluted in phosphate buffer stabilized with 0.09% sodium azide), and the turbidity is measured at a wavelength of 340 nm. The absorbance increase is directly proportional to the concentration of apo A‐I 19.…”

Familial resemblance of plasma apolipoprotein B: The Nancy study

“…Apo B level was measured in whole plasma, on a Cobas-Bio centrifugal analyzer (Roche Diagnostic) using immunoturbidimetric assays [Rifai and King, 19861. The immunoturbidimetric method has been shown to yield reliable results for routine assays of apo B, not only in normolipemic, but also in hyperlipemic sera [Siedel et al, 1988). The change in turbidity of the sample against a reagent blank was measured at 340 nm after 0.5 and 360 sec of incubation at 37°C.…”

Comparison Of Immunonephelometric And Immunoturbidimetric Methods for Measuring Beta 2-Microglobulin: Fit for Purpose in Routine Clinical Laboratories

“…There are many studies in the literature which compared the results of different spesific proteins, such as CRP, IgA, IgG, IgM, C3, C4, haptoglobin, transferin, apolipoproteins, RF etc. held by nefelometric and turbidimetric methods, and results of two methods were found to be correlated with each other [21,[28][29][30][31][32]. Correia et al [28] found that CRP levels measured by either methods were correlated with each other, in both unstable angina patients and in patients with non-ST elevation acute myocardial infarction.…”