Method for determining complex prostatic specific antigen (cPSA) and test kit for use in carrying out the method

摘要

In the present invention, there is disclosed a method for determining the complexed forms of immunologically determinable prostate specific antigen (cPSA) in a blood sample, e.g., by two-site immunometric assays, in which the blood sample is treated to render free PSA (fPSA) immunologically nondetectable. A particularly preferred immunometric assay method employs three anti-PSA antibodies: an antibody that binds to both cPSA and fPSA (anti-tPSA), a second anti-tPSA antibody which is characterized by the unique property that binding to fPSA is blocked by binding of fPSA-specific antibodies, and a third antibody which is a fPSA-specific antibody. Thus, binding of the fPSA-specific antibody to PSA in the sample allows only cPSA to be measured in the immunometric assay. Disclosed is also a test kit for use in determining cPSA in a blood sample, comprising: (1) a first anti-PSA antibody, which binds to tPSA, (2) a second anti-PSA antibody, which binds to tPSA, but which is substantially incapable of binding to PSA when PSA is bound by an antibody that binds to fPSA but not to cPSA, wherein one of said first and second antibodies is labeled and the other is immobilized or capable of being immobilized for purposes of separation from an aqueous liquid test mixture, and (3) a third anti-PSA antibody, which binds to fPSA but not to cPSA.