F-PSA

AcronymDefinition
F-PSAForm of Prostate-Specific Antigen
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Positive detection rates of tumour markers were: CA19-9 (49.3%), CA125 (45.1%), FER (44.2%), CA242 (42.5%), CEA (38.6%), CA15-3 (36.7%), beta-HCG (29.6%), AFP (24.5%), NSE (18.2%), PSA (19.5%), f-PSA (9.4%) and HGH (8.7%) respectively.
Similarly, attempts to use the percentage of f-PSA, as the ratio of f-PSA:t-PSA, to provide improved discrimination between BPH and prostate cancer, will be flawed in the absence of the inclusion of PSA-AMG in what constitutes t-PSA, i.e., with t-PSA underestimated, the percent of f-PSA will be higher, directing suspicion, in accord with present guidelines, away from possible prostate cancer.
Of these, H117 and H50 recognize both free and complexed PSA, whereas 5A10 recognizes only F-PSA (26).
It was later shown that PSA-ACT was somewhat unstable when stored in buffers at pH 7.5 and 35 [degrees]C over several weeks, releasing F-PSA measurable by an immunological assay (20).
We recently used this assay along with measurements of t-PSA (Bayer Immuno-1), f-PSA (Abbott IMx; Abbott Diagnostics), and the ratio of f-PSA to t-PSA (Abbott IMx, both assays) on a prospective basis in men referred to a hospital urology clinic with t-PSA measurements between 3.0 and 22.0 [micro]g/L.
Several studies have shown that the ratio of f-PSA to total PSA (t-PSA; i.e., free + ACT-bound PSA) is lower in prostate cancer patients than in BPH patients (9, 10).
AxSYM PSA and AxSYM Free PSA (Abbott Diagnostics), automated microparticle enzyme immunoassays, were used for measuring t-PSA and f-PSA, respectively [7].
In this study we investigated assay systems (i.e., f-PSA and the corresponding t-PSA assay) from four different manufacturers.
PSA exists primarily in two immunoreactive forms: a ~33-kDa monomer (F-PSA) and a ~100-kDa complex with the protease inhibitor [[alpha].sub.1]-antichymotrypsin (PSA-ACT).
This activity is held to be essential for formation of the PSA-ACT complex [20,21], implying that antibodies that affect the activity may be associating with epitopes proximate to the ACT binding site, and may therefore have special properties, such as the ability to distinguish f-PSA from the complex.