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The Cholestech LDX aspartate aminotransferase (AST) test is for the in vitro quantitative determination of AST in whole blood or serum on the Cholestech LDX Analyzer. AST measurements are used in the diagnosis and treatment of certain liver diseases (e.g., viral hepatitis and cirrhosis), and heart diseases.

The Cholestech LDX System combines enzymatic methodology and solid-phase technology to measure AST. Samples used for testing can be whole blood from a fingerstick (collected in a lithium heparin coated capillary tube), venous whole blood or serum. The sample is applied to a Cholestech LDX AST cassette. The cassette is then placed into the Cholestech LDX Analyzer where a unique system on the cassette separates the plasma from the blood cells. The plasma flows to both sides of the cassette and is transferred to the AST reaction pad. The Cholestech LDX Analyzer measures Aspartate aminotransferase by an enzymatic method based on the method formulation of Katsuyama et al. 12- Aspartic acid aminotransferase catalyzes the transfer of amino groups from L-Aspartic acid to alpha-Ketoglutarate producing oxaloacetate and glutamate. Oxaloacetate Decarboxylase converts the Oxaloacetate to Pyruvate by the removal of CO2. Pyruvate oxidase, in the presence of oxygen, oxidizes the pyruvate to acetylphosphate and hydrogen peroxide. In a reaction catalyzed by horseradish peroxidase, the peroxide reacts with an indicator dye to form a blue color at a rate proportional to the AST concentration of the sample. The resultant color in the reaction is measured by reflectance photometry. A brown magnetic stripe on each cassette contains the calibration required for the Cholestech LDX Analyzer to convert the reflectance reading to the AST concentration in U/L. 37°C.