In prostate tests PSA what is the difference between total PSA and free PSA?
What is the normal range? In addition, how can it be that if there is ANY prostate
specific antigen in the blood that there is no prostate cancer?
Doesn’t the existence of any PSA means that the body is reacting with antibodies
against cancerous cells in the prostate.
PSA starts out in the fluid that carries sperm. PSA is a protein normally made in
the prostate gland in ductal cells. These cells make some of the semen that comes
out of the penis during sexual climax (orgasm). PSA helps to keep the semen
liquid.
PSA is measured by nanograms per millimeter of blood. Most men have under 4
nanograms. Anything higher can indicate prostate cancer. PSA traveling alone is
called free PSA. The free-PSA test measures the percentage of unbound PSA.
Rather than subject everyone with an elevated PSA to a biopsy, some urologists
measure free PSA in patients with a total PSA level between 4 ng/ml and 10 ng/ml.
A PSA level of 4 to 10 ng/ml is considered slightly elevated levels between 10 and
20 ng/ml are considered moderately elevated; and anything above that is
considered highly elevated. The presence of PSA does not necessarily mean that
the body is reacting against cancer cells Other conditions can affect PSA:
* Prostatitis and Lower Urinary Tract symptoms (LUTS) can elevate PSA
* BPH (benign hypertrophy or enlargment of the prostate) can elevate PSA
* Prostate cancer (PCa) often elevates PSA but not always. Some of the most
aggressive types of prostate cancer do NOT make or "leak" high levels of PSA.
Prostatitis and BPH are much commoner than prostate cancer.
Source(s): /> /> />PSA is a protein produced by the cells of the prostate gland. The most frequently
used PSA - prostate-specific antigen test - is the total PSA, which measures the
sum of the free PSA and the cPSA (complex or bound) in the blood. When a doctor
orders a “PSA test,” he is referring to a total PSA. When the prostate gland
enlarges, PSA levels in the blood tend to rise. PSA levels can rise due to cancer or
benign (non cancerous) conditions. Because PSA is produced by the body and can
be used to detect disease, it is sometimes called a biological marker or tumour
marker. The PSA level that is considered normal for an average man ranges from 0

should be consulted for diagnosis and treatment of any and all medical conditions.
I add a link with details of this subject

understanding/analytes/psa/test.html
Intermethod Differences in Results for Total PSA, Free PSA, and Percentage
of Free PSA
Patricia R. Slev, PhD; Sonia L. La'ulu; William L. Roberts, MD, PhD
Authors and Disclosures
Posted: 06/25/2008; American Journal of Clinical Pathology. 2008;129(6):952-958. © 2008
American Society for Clinical Pathology
Abstract
Serum prostate-specific antigen (PSA) assays differ in calibration and response to different PSA
forms. We examined intermethod differences in total PSA (tPSA) and free PSA (fPSA)
measurements. We tested 157 samples with tPSA concentrations of 2 to 10 ng/ mL (2-10 µg/L)
using 6 PSA/fPSA method pairs and 1 tPSA method: ADVIA Centaur (complexed and total;
Siemens Diagnostics, Tarrytown, NY), ARCHITECT i2000
SR
(Abbott Diagnostics, Abbott Park,
IL), AxSYM (Abbott Diagnostics), IMMULITE 2000 (Siemens Diagnostics), Modular E170
(Roche Diagnostics, Indianapolis, IN), UniCel DxI 800 (Beckman Coulter, Brea, CA), and
VITROS ECi (tPSA only; Ortho- Clinical Diagnostics, Raritan, NJ). Regression analysis was
performed for PSA, fPSA, and percentage of fPSA with the ARCHITECT i2000
SR
comparison
method. Differences between test and comparison methods were estimated at 2.5, 4.0, and 10.0
ng/mL (2.5, 4.0, and 10.0 µg/L) for tPSA and 15%, 20%, and 25% for percentage of fPSA.
Relative differences were more than 10% at 4.0 ng/mL (4.0 µg/L) tPSA for the Centaur,
IMMULITE, ECi, and DxI methods. At 20% fPSA, the relative difference was more than 10% for
all methods except the AxSYM. Additional harmonization is needed for tPSA and fPSA methods.
Introduction

from detection or whether these are the patients who have indolent forms of prostate cancer.
Therefore, recommendations indicate that a biopsy should be performed in any patient with a
tPSA result that is greater than 10.0 ng/mL (10.0 µg/L), and further investigation is warranted in
patients who are in the diagnostic gray zone and have a result between 4.0 and 10.0 ng/mL (4.0-
10.0 µg/L) tPSA.
[5-9]
In high-risk populations, a biopsy is recommended if the tPSA is 2.5 ng/mL
(2.5 µg/L) or more.
[3]
It has been recently suggested that this lower tPSA cutoff should be
adopted for screening men of all ages.
[10]
Although the medical decision points for percentage of
fPSA are also equally controversial, it is generally accepted that measuring fPSA and calculating
the percentage of fPSA aids in distinguishing cancer from other benign prostate conditions such
as benign prostate hyperplasia, particularly for the population in the diagnostic gray zone.
[3,11,12]
The lower the fPSA/tPSA ratio, the greater the likelihood of cancer.
[11]
Currently, biopsy is
recommended for 15%, 20%, or 25% fPSA.
[11,13,14]

Third, PSA measurements are further complicated by the fact that different assays measure
different PSA isoforms to varying extents. Although a certain amount of variation is inevitable
because different methods have antibodies that recognize different epitopes of PSA, ideally,
assays that measure tPSA should be equimolar and unbiased in the detection of free and
complexed PSA. Historically, however, different assays have produced significantly different
results for PSA on the same sample. Although lack of an equimolar response was in part
responsible for this phenomenon, the other problem was the lack of calibration against a