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
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).
Recently, several reports have shown the ratio between F-PSA
and total PSA (T-PSA) values in serum (21-27).
, and ACT-PSA were measured on an ES immunoanalyzer (Boehringer Mannheim GmbH).
AxSYM PSA and AxSYM Free PSA (Abbott Diagnostics), automated microparticle enzyme immunoassays, were used for measuring t-PSA and f-PSA
, respectively .
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.