Time-Resolved Immunofluorometric Assay for the Quantification of Lipoprotein(a) in Serum

Summary: Although two recent studies have failed to reveal lipoprotein(a) (LP(a)) serum concentrations> 300 mg/1 to be an independent risk factor for early onset of atherosclerosis, Lp(a) serum concentrations are frequently measured to evaluate the additional risk of coronary heart disease. We describe a time-resolved immu-nofluorometric assay (TRIFMA) for quantifying Lp(a) levels in human serum using commercially available rea-gents, which is rapid, robust and simple to perform. The two-site immunometric assay was based on microtitre plates as solid phase coated with a polycloncal anti Lp(a) antibody. The liquid-phase antibody was labelled with biotin and detected by europium labelled streptavidin in the DELFIA 1232 fluorometer. The measuring range was 2-1600 mg/1. The intra-assay imprecision was < 7 % (CV), the inter-assay imprecision < 12 % (CV). No interfer-ence was detected with plasminogen concentrations up to 2.2 g/1. There was an acceptable correlation with a commercially available enzyme immunoassay (r = 0.95) and with electroimmunodiffiision (r = 0.85) on 100 routine serum samples measured. The assay appeared to detect different Lp(a) isoforms as dilution curves were parallel for B/F, S2 and S4 isoforms