Mk. Terris et Ta. Stamey, UTILIZATION OF POLYCLONAL SERUM PROSTATE-SPECIFIC ANTIGEN LEVELS IN SCREENING FOR PROSTATE-CANCER - A COMPARISON WITH CORRESPONDING MONOCLONAL VALUES, British Journal of Urology, 73(1), 1994, pp. 61-64
Objectives Prostate specific antigen (PSA) measurement has become incr
easingly popular as a screening test for prostatic adenocarcinoma. Alt
hough this is a sensitive, organ-specific assay, use as a screening to
ol is hampered by the lack of a clearly defined normal range in older
men, frequent elevation of PSA levels by benign processes, and the ava
ilability of two different assays, one polyclonal and the other monocl
onal, which produce very different values. This study was designed to
evaluate the distribution of PSA levels by the Yang and corresponding
Hybritech values in patients from the general population. Subjects and
methods A total of 478 volunteers over 40 years of age underwent seru
m PSA determination by the Yang polyclonal radioimmunoassay and digita
l rectal examination. The PSA levels were stratified and the patient d
istribution analysed. Results In 69% of patients, PSA levels were less
-than-or-equal-to 2.5 ng/ml (proposed normal range for the Yang polycl
onal assay). In 89% of patients, PSA levels were less-than-or-equal-to
7.3 ng/ml by the polyclonal assay which corresponds approximately to
the proposed normal range of 0-4.0 ng/ml by the Hybritech monoclonal a
ssay. Nine per cent of patients fell between 7.4 and 18.4 ng/ml by the
polyclonal assay (4.1-10 ng/ml by the monoclonal assay) and 2% had po
lyclonal PSA levels > 1 8.4 ng/ml ( > 1 0 ng/ml by the monoclonal assa
y). Cancer detection rates (influenced by the percentage of patients u
ndergoing biopsy) were 0.3% in patients with polyclonal PSA levels les
s-than-or-equal-to 2.5 ng/ml, 1.2% in patients less-than-or-equal-to 7
.3 ng/ml, 20.9% between 7.4 and 18.4 ng/ml, and 50% of those >18.4 ng/
ml; the overall cancer detection rate was 3.8%. Conclusions These data
support the use of higher PSA levels as a criterion for further evalu
ation in screening for prostate cancer and establish the frequency dis
tribution of PSA in a screening population when the Yang assay is used
.