With current assays for PSA, the actual amount of t-PSA
The CVs based on calculated concentration for the calibrators were between 15% and 1.5% for F-PSA (F-PSA, 0.09-249 [micro]g/L) and between 22% and 2.6% for T-PSA (T-PSA, 0.51-257 [micro]g/L) as shown in Fig.
The analytical recovery was studied by adding purified PSA-ACT to male and female serum samples to a final concentration of 10 [micro]g/L, and performing the assay to determine the T-PSA concentration in the samples with and without added PSA-ACT.
Plasma from a patient with CaP (T-PSA, 1890 [micro]g/L; F-PSA, 190 [micro]g/L) and reference sera were obtained from Bioclinical Partners Inc.
At the end of the incubation, the samples were analyzed by reversed-phase HPLC and the ENZYMUN[R] assays for F-PSA and T-PSA.
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.
 Nonstandard abbreviations: PSA, prostate-specific antigen; BPH, benign prostatic hyperplasia; ACT, [[alpha].sub.1]-antichymotrypsin; A2M, [[alpha].sub.2]-macroglobulin; f-PSA, free PSA; t-PSA
, total PSA; mAb, monoclonal antibody; PBS, phosphate-buffered saline; PBS-T, PBS-Tween 20; BSA, bovine serum albumin; TBS, Tris-buffered saline; and TBS-T, TBS-Tween 20.
These observations raise the possibility that a skewed assay might correlate well with an equimolar assay when the proportion of F-PSA to T-PSA (F/T) in serum is low.
The T-PSA concentration measured by the equimolar assays is nearly equal to the sum obtained by the PA313/ FPA503 and [alpha]ACT/PA313 (F-PSA + C-PSA), whereas the T-PSA concentration measured by the IMx assay is higher than F-PSA + C-PSA.
, f-PSA, 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.