Abstract: A method is provided, in one embodiment, for the determination of an analyte in a biological fluid sample in the presence of a substance interfering with an assay for the analyte. This embodiment is implemented by using antibodies to cause the selective immunoreaction of at least one of the analyte or the interfering substance and then conducting an assay for the analyte in at least one of the immunoreactants or the non-reactants. Another embodiment provides a disposable reaction device to implement the method. The invention is applicable to the detection of a wide variety of analytes, including cholesterol in a targeted lipoprotein class in the presence of cholesterol in another class; to targeted isozymes of enzymes such as creatine kinase, lactate dehydrogenase, amylase, and alkaline or acid phosphatases in the presence of other isozymes; as well as to targeted immunoglobulins in the presence of non-targeted immunoglobulins.

Abstract: A method is provided for preparing lipoprotein (a) from a volume of biological fluid that is substantially free of lipoproteins of another class. The method involves an ultracentrifugation step in which at least one fraction is recovered that contains Lp(a). This material is then reacted with immobilized ligand to remove non-Lp(a) interfering substances from the fraction, the Lp(a) remaining unbound. The non-reacted Lp(a) is subsequently obtained in a form that is suitable for use in the analysis of any of protein concentration, protein isoform determination or cholesterol assays. A method of identifying and measuring an amount of one or more isoforms of Lp(a) is further provided.

Abstract: A method is provided, in one embodiment, for the determination of an analyte in a biological fluid sample in the presence of a substance interfering with an assay for the analyte. This embodiment is implemented by using antibodies to cause the selective immunoreaction of at least one of the analyte or the interfering substance and then conducting an assay for the analyte in at least one of the immunoreactants or the non-reactants. Another embodiment provides a disposable reaction device to implement the method. The invention is applicable to the detection of a wide variety of analytes, including cholesterol in a targeted lipoprotein class in the presence of cholesterol in another class; to targeted isozymes of enzymes such as creatine kinase, lactate dehydrogenase, amylase, and alkaline or acid phosphatases in the presence of other isozymes; as well as to targeted immunoglobulins in the presence of non-targeted immunoglobulins.