Abstract
Objectives. The determination of the percentage of free prostate-specific antigen
(%fPSA) enhances the specificity of prostate cancer (CaP) detection. This study was
undertaken to assess the performance of %fPSA in differentiating benign prostate disease
from CaP and to determine the CaP probability estimates using the AxSYM Free PSA and
AxSYM Total PSA assays.
Methods. In this prospective study, 297 men, 50 years old or older, with a total PSA
level between 4 and 10 ng/mL and a nonsuspicious digital rectal examination were enrolled
at 10 clinical sites. All subjects underwent at least sextant prostate biopsies to
establish the diagnosis. fPSA and total PSA (tPSA) levels were determined using the
AxSYM Free PSA and AxSYM Total PSA assays. Percent fPSA values were compared with
tPSA values to determine the appropriate cutoffs for prostate biopsy and to calculate
the CaP probability estimates.
Results. The strongest predictor of CaP in a logistic regression model was %fPSA (odds
ratio 2.29), which contributed significantly more than age or tPSA to the predictive
model. In this study population, a %fPSA cutoff of 26.4% would have detected 96% of
subjects with CaP (sensitivity) and would have eliminated 27.4% of unnecessary biopsies
(specificity). CaP probability estimates ranged from 9% to 69% and increased as the
%fPSA value decreased. Men with a %fPSA level of 10% or lower had a 69% probability
of CaP, and men with a %fPSA level of greater than 26% had a 9% probability of CaP.
Conclusions. Percent fPSA values can help differentiate CaP from benign prostate disease
and reduce unnecessary biopsies in 27% of men 50 years old or older whose digital
rectal examination was normal and whose tPSA level was between 4 and 10 ng/mL. A %fPSA
result can assist the physician and patient in determining the probability of CaP
and assessing the need for prostate biopsy.
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Article info
Publication history
Accepted:
January 3,
2000
Received in revised form:
January 3,
2000
Received:
August 23,
1999
Footnotes
☆This study was funded through a grant provided by Abbott Laboratories.
Identification
Copyright
© 2000 Elsevier Science Inc. Published by Elsevier Inc. All rights reserved.
