Developments and clinical evaluations of easy-to-perform and rapid measurements of serum Lp(a) concentrations and apo(a) isoforms.

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Although several different techniques to determine serum lipoprotein(a) (Lp(a)) were developed, many laboratories still lack reliable any easy-to-perform assay for Lp(a) measurements. At present, ELISA method is the most commonly used technique to measure serum Lp(a), because it is highly sensitive, specific in principle, and does not require radio-isotopes. Gowever, the ELISA method requires highly diluted serum as samples, measurement in duplicate to achieve satisfactory precision, and several hours for the assay. The immunonephelometric and immunoturbidimetric assays are suitable for the clinical laboratories, in that they are rapid and easy-to-perform, have a high throughput, and can be automated. The turbidimetric immunoassay (TIA) and latex-enhanced immunoassay (LIA) methods, however, also are sensitive to differences in size of the analyte being measured. After the careful evaluations, we have chosen automated procedure for Lp(a) measurement by an LIA method having satisfactory precision, specificity and sensitivity.On the other hand, a new system has been employed to determine the apo(a) phenotypes. After electrophoresis and immunoblotting, Rf values of apo(a) isoform bands were measured using a computerized digital micro scale and apo(a) phenotypes were categorized automatically based on the Rf values. Recently, in an attempt to classify the apo(a) genotypes, we have investigated the basis of the apo(a) size polymorphism by pulsed-field gel electrophoresis of genomic DNA employing the restriction enzymeKpnI and an apo(a) kringle IV specific probe.