T. Okegawa et al., Comparison of two investigative assays for the complexed prostate-specificantigen in total prostate-specific antigen between 4.1 and 10.0 ng/mL, UROLOGY, 55(5), 2000, pp. 700-704
Objectives. To determine the ability of complexed prostate-specific antigen
(cPSA) levels to diagnose prostate cancer.
Methods. Between September 1998 and March 1999, cPSA levels in 182 consecut
ive patients with an abnormal digital rectal examination (DRE) or a total P
SA (tPSA; Tandem-R assay) level greater than 4.1 ng/mL were examined. Level
s of cPSA were measured by the Markit-M PSA-ACT (alpha(1)-antichymotrypsin)
assay (cPSA-MM) and Bayer Immune 1 complexed PSA assay (cPSA-BI). Free PSA
(fPSA) was measured by the Tandem-R free PSA assay.
Results. Of the 140 patients with tPSA between 4.1 and 10.0 ng/mL, 116 were
histologically confirmed as having benign tissue; the remaining 24 were di
agnosed with prostate cancer. To ensure a 92% sensitivity of cancer detecti
on, a cutoff value for the tPSA, cPSA-MM, and cPSA-BI assays of 4.8 ng/mL,
2.7 ng/mL, and 4.6 ng/mL, respectively, was determined. The percentage of n
egative biopsies prevented at these cutoff (ie, specificity) values was 14%
, 23%, and 24%. No significant differences among these three assays were fo
und. At 92% sensitivity, the cutoff value for the fPSA/tPSA, fPSA/cPSA-MM,
and fPSA/cPSA-BI ratios was 18%, 27%, and 18%, respectively. The specificit
y was 35%, 49%, and 51%. No significant differences were found among these
three fPSA ratios. Significant differences were noted between tPSA and the
fPSA/cPSA-MM ratio and between tPSA and the fPSA/cPSA-BI ratio. No differen
ces were seen among the other PSA parameters.
Conclusions. No difference in the ability of cPSA levels to distinguish pro
state cancer and noncancer was observed between cPSA-MM and cPSA-BI or betw
een their fPSA ratios. Only the fPSA/cPSA-MM and fPSA/cPSA-BI ratios provid
ed significantly enhanced diagnostic performance compared with tPSA. UROLOG
Y 55: 700-704, 2000. (C) 2000, Elsevier Science Inc.