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Enzymes and Protein Markers |
1
Centro Nazionale Applicazione Biotecnologie in Oncologia and
2
Division of Urology, Regional Hospital, 30122 Venice, Italy.
3
Urology Clinic, University of Padua, 35128 Padua, Italy.
4
Central Laboratory, Regional Hospital, 35128 Padua,
Italy.
5
Central Laboratory, Le Molinette Hospital, 10100 Turin,
Italy.
6
Urology Clinic, University of Turin, 10100 Turin, Italy.
7
Urology Clinic and
8
Nuclear Medicine Unit,
University of Sassari, 07100 Sassari, Italy.
9
Central Laboratory and
10
Division of
Urology, Regional Hospital, 31100 Treviso, Italy.
a Address correspondence to this author at: Centro Regionale Indicatori Biochimici di Tumore, Ospedale Civile, 30122 Venezia, Italy. Fax 39-41-5294532; e-mail cnabo{at}provincia.venezia.it.
Although general consensus exists that percent free prostate-specific
antigen (PSA) is superior to total immunoreactive PSA for prostate
cancer (CaP) detection, its diagnostic performance is not yet well
established. Analytical problems may account for difficulties in
evaluating percent free PSA because the free PSA concentration is
substantially lower than that of total PSA. The aim of the present
study was to establish the diagnostic performances of the
IMMULITE percent free PSA assay from Diagnostics Products Corp.
under experimental conditions optimized to minimize analytical
variability. Eighty-five patients with untreated primary CaP and 261
with untreated benign prostate hypertrophy (BPH) were prospectively
enrolled. The Diagnostics Products IMMULITE total (Third
Generation) and free PSA were measured by the same technician, using
the same instrument and the same reagent batch. We calculated the
post-test probability to express how the likelihood of the diagnosis of
CaP changed after the percent free PSA was determined. Areas under the
ROC curves of percent free PSA were better than those of total PSA in
every evaluated range of total PSA. The percent free PSA could have
reduced the rate of unnecessary biopsies by 47% in patients with total
PSA 
4 µg/L with only 3.8% false-negative results. The post-test
probability of percent free PSA was, however, <50% in men 50–70
years of age, using cutoff points providing sensitivity from 99% to
80%. Percent free PSA is superior to total PSA in distinguishing
primary CaP from BPH in patients with total PSA between 2 and 30
µg/L. In men with low total PSA, the diagnostic performance of the
percent free PSA assay may be optimized by controlling methodological
variability. The percent free PSA assay is effective in reducing the
rate of unnecessary biopsies in men with total PSA >4 µg/L. However,
the post-test probability provided by percent free PSA is relatively
low in asymptomatic patients 50–70 years of age.
The following articles in journals at HighWire Press have cited this article:
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  S. A.R. Kort, F. Martens, H. Vanpoucke, H. L. van Duijnhoven, and M. A. Blankenstein Comparison of 6 Automated Assays for Total and Free Prostate-Specific Antigen with Special Reference to Their Reactivity toward the WHO 96/670 Reference Preparation Clin. Chem., August 1, 2006; 52(8): 1568 - 1574. [Abstract] [Full Text] [PDF]
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K. Jung, U. Elgeti, M. Lein, B. Brux, P. Sinha, B. Rudolph, S. Hauptmann, D. Schnorr, and S. A. Loening Ratio of Free or Complexed Prostate-specific Antigen (PSA) to Total PSA: Which Ratio Improves Differentiation between Benign Prostatic Hyperplasia and Prostate Cancer? Clin. Chem., January 1, 2000; 46(1): 55 - 62. [Abstract] [Full Text] [PDF]
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 M. L. Beckett, L. H. Cazares, A. Vlahou, P. F. Schellhammer, and G. L. Wright Jr. Prostate-specific Membrane Antigen Levels in Sera from Healthy Men and Patients with Benign Prostate Hyperplasia or Prostate Cancer Clin. Cancer Res., December 1, 1999; 5(12): 4034 - 4040. [Abstract] [Full Text] [PDF]
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