FREE AND COMPLEXED PROSTATE-SPECIFIC ANTIGEN IN THE DIFFERENTIATION OF BENIGN PROSTATIC HYPERPLASIA AND PROSTATE-CANCER - STUDIES IN SERUM AND PLASMA SAMPLES
F. Espana et al., FREE AND COMPLEXED PROSTATE-SPECIFIC ANTIGEN IN THE DIFFERENTIATION OF BENIGN PROSTATIC HYPERPLASIA AND PROSTATE-CANCER - STUDIES IN SERUM AND PLASMA SAMPLES, The Journal of urology, 160(6), 1998, pp. 2081-2088
Purpose: We prospectively evaluated serum and plasma concentrations of
total and free prostate specific antigen (PSA), and PSA complexed to
al-antichymotrypsin in 170 patients who underwent biopsy, including 59
with prostate cancer and 111 with benign prostatic hyperplasia. We co
mpared the usefulness of the ratios of free-to-total and complexed-to-
total PSA for distinguishing between prostate cancer and benign prosta
tic hyperplasia, and studied the influence of blood clotting on the ra
tios. Materials and Methods: Blood samples were processed to generate
serum and citrated plasma. To calculate complexed-to-total and free-to
-total PSA we assayed plasma and serum samples for total and complexed
PSA using homemade immunoassays, and total and free PSA using the Imm
ulite assay. The 2 total PSA assays were compared using the Tandem-E
dagger PSA assay. Receiver operating characteristics curves were const
ructed for the total population, and for 2 to 20, 4 to 20, 2 to 10 and
4 to 10 ng./ml. total PSA. Results: In all groups complexed-to-total
PSA had higher specificity than free-to-total and total PSA, especiall
y at 90 to 100% sensitivity. Generally citrated plasma samples provide
d higher specificity than serum samples for all sensitivity values. Th
e best performance for complexed-to-total and free-to-total PSA was ob
tained in the subset of patients in whom total PSA was 2 to 10 ng./ml.
Conclusions: Our results indicate that the complexed-to-total PSA rat
io performed better for classifying disease status than the free-to-to
tal PSA ratio in the whole patient population and in the diagnostic gr
ay zone of 2 to 10 ng./ml. In addition, plasma samples should be used
to calculate the complexed-to-total and free-to-total PSA ratio.