Abstract: An assay for determining the presence of a threshold concentration of an analyte in a sample comprises first reacting the sample with an amount of anti-analyte selected to reduce the free analyte to a marginally detectable concentration. The sample is then contacted with anti-analyte immobilized on a test region or indicator zone on a solid phase, whereby the residual free analyte may be bound. The binding of free analyte to immobilized anti-analyte is detected by a variety of techniques to indicate the presence of the threshold concentration. By employing limited amounts of anti-analyte on the solid phase, the change between maximum binding of label and no binding of label will be responsive to very small changes in the analyte concentration originally present in the sample.

Abstract: A method for isolating nucleated fetal erythrocytes (NFEs) from a maternal blood sample by separating erythrocytes in the maternal blood sample from all other nucleated cells therein using a leukocyte depletion device; and isolating NFEs from nonnucleated maternal erythrocytes. Preferably the maternal blood is peripheral maternal blood. The isolated NFEs can then be analyzed for genetic disorders and the like, such as by in situ hybridization.

Abstract: A method of quantitative assay for a substrate such as triglyceride capable of undergoing enzymatic hydrolysis to release long chain fatty acids in an albumin-containing clinical sample comprises incubating the albumin-containing clinical sample with an enzyme such as lipase which acts upon the substrate to be assayed under conditions effective to release fatty acid therefrom, causing the fatty acid thus released to bind to a fatty acid binding protein (FABP) and assaying the binding of the fatty acid to the FABP.

Abstract: The present invention provides for novel homogeneous immunoassay systems involving complement-mediated lysis of marker-encapsulating lipid vesicles (liposomes) for detection of analyte in a fluid sample. These systems do not require the separation of unbound antigens and/or antibody conjugates yet provide highly sensitive procedures for analyte detection. Liposomes containing a marker, are coupled to antibody fragments in a way which confers the liposomes with immunological specificity yet avoids sensitizing the liposomes to complement mediated lysis in the absence of analyte. Antibody sensitized liposomes (the first reagent) are sequentially incubated with an analyte-containing sample, and optionally "dummy" liposomes, which do not contain encapsulated marker, a second antibody (the second reagent), and finally with a complement source such as plasma. Complement is activated by the liposome-antibody-antigen-second antibody complex causing liposome lysis and a concomitant release of marker.

Abstract: Methods for distinguishing multiple subpopulations of biological particles in a single sample based upon quantitative differences in the fluorescence intensity attributable to one or two fluorochromes with which the biological particles are labelled. The method is used with flow cytometric particle counting techniques to count and sort and biological particles such as the formed elements of blood and other tissue cells. Also disclosed are reagents containing fluorochrome-conjugated antibodies used in the methods.