A novel assay for the quantitative determination of lipoprotein-X (LP-X) in serum

A new, fast and simple quantitative LP-X assay is described. The method selectively removes apoB-containing lipoproteins by precipitation with specific antibodies. To the supernatant, a precipitation system for LP-X, viz. SDS and MgCl2 in final concentrations of 0.5 g/l and 0.2 mol/l respectively, is added and the turbidity measured at 360 nm. The assay is linear from 0.2 g/l-5.0 g/l and shows a high precision (inter-assay CV of less than 3%). The test correlates favourably with other quantitative LP-X assays, but has the particular advantage that it can be automated and that the time required for one series is only 2 h.