Methods for measuring serum psa

Serum PSA is now mostly determined by immunoassays—more specifically two-site immunometric "sandwich" assays. In these methods, commercially available from many suppliers for manual or automated assay systems, two separate antibodies to PSA are incubated with the sample. In heterogeneous assays, one antibody is conjugated to immobilized surface, including various types of particle, and the other antibody is, directly or indirectly, conjugated to a reporter molecule. The reporter molecule can provide a colori-metric, fluorescence, or chemiluminescense signal directly or through an enzyme-linked immunosorbent assay (ELISA) pathway. The bound reporter molecules with PSA sandwiched between the immobilized and the reporter antibodies) are separated, washed (if needed), and expressed into the relevant signal. Thus, the signal is directly proportional to the PSA present in the sample. Among the commercially available automated immunoassay methods to measure PSA in human serum, there are the magnetic particle chemilumi-nescence assay (CLIA), the microparticle enzyme assay, electrochemiluminescence assay, and radioimmunoassay. The antibody pairs used in these assays could be both monoclonal or polyclonal, or a monoclonal-polyclonal combination. Technical factors like assay design and components used do affect the assay results and, thus, the clinical utility of PSA results.

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