PSA
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PSA BLOOD TEST

Prostate-specific antigen (PSA) is a protein produced by cells of the prostate gland or of prostate cancer. The PSA test measures the level of PSA in the blood. The code for a screening PSA for a Medicare beneficiary is G0103. The correct code for a diagnostic PSA test to monitor disease is 84153.

What is your elevated PSA and what does it mean?

PSA testing is not an exact science. PSA is produced by three things, benign prostate growth, prostatitis (infection/inflammation) or prostate cancer.  The amount of PSA produced by benign tissue can be roughly approximated by multiplying the gland volume (cc or grams) by 0.066 {Dr. Strum} or 0.1 {Dr. Bahn}, as an upper limit.  The gland volume can be estimated by a very skilled doctor during the Digital Rectal Exam or from a transrectal ultrasound (TRUS).

If the PSA is elevated above this value, further evaluation is suggested. You should make sure that PSA tests are processed by the same lab each time, using the same assay (Examples: Abbott, Hybritech [Tandem E], Tosoh, DPC [Immulite] or Beckman Coulter [Access]).  We suggest you avoid irritation to the prostate in the 24-48 hours before the blood is drawn such as: Rectal Exams, ejaculation, bicycle rides, etc.

While many labs list 0-4.0 as normal PSA, some of the most aggressive forms of prostate cancer release low amounts of PSA into the blood stream. It is important to consider the PSA Velocity(rate of change over time). An increase of more than 0.4 in a year should be considered suspicious.

Related resources:

The PCRI Views Regarding Testing for Prostate Cancer
Using PSA Intelligently to Manage Prostate Cancer, Part 1&2

Can other factors affect the PSA reading?

Other factors that studies have been suggested to affect the PSA:

  • The “normal” PSA reading for obese men may be lower due to the dilution from a larger quantity of blood.
  • Finasteride (Proscar 5mg or Propecia 1mg) or dutasteride (Avodart) can lower PSA 40-50%.
  • A study in France suggested PSA values are related to amount of sunshine and are higher in summer than in winter. {Salama Seasonality of serum prostate-specific antigen levels: a population-based study, Eur Urol. 2007 Sep;52(3):708-14}
  • Taking aspirin or other commonly used painkillers can lower blood levels of prostate-specific antigen (PSA). A similar lowering effect was seen for regular use of acetaminophen (Tylenol), although it did not reach statistical significance.
  • PSA levels declined by a statistically significant extent after initiation of treatment with a statin drug.
  • The types of infections that might cause an elevation in one’s PSA are things like pneumonia, phlebitis, a blood clot, somebody who is septic, a urinary tract infection.  There is not usually a PSA increase with a cold/respiratory virus.

 

What other PSA data is relevant?

Free and Complex PSA
Most PSA is attached to blood proteins (complex or bound) but some is not attached (free). The ratio of free-to-total PSA has been found useful for evaluating the risk of cancer, particularly in the range of 4-10 ng/ml. Some Urologists believe that a F/T ratio of less than 10% is a reason to biopsy but again, there are many variables and we are not talking about an exact science. A low free/total PSA ratio is not always a good indicator because both prostatitis and prostate cancer can result in a low ratio.

PSA Velocity (PSAV)
As mentioned previously, there are many factors that impact the value of a PSA level. The rate of change over time, PSAV, should be monitored. Annual increases ≥ 0.4 ng/ml should be evaluated for infection or cancer.  A PSAV of greater than 2.0 per year has been suggested as a poor prognostic indicator by one study. You can input your PSA values with dates to calculate PSAV at:
PSAV Calculator from Memorial Sloan Kettering

PSA Doubling Time (PSADT)
PSADT is a calculation of the time it takes for the PSA value to double. This should be based on at least three values separated by at least three months each; before diagnosis. A PSADT of less than 10 years may be an indication of the presence of PC. PSADT is best calculated with a mathematical log-slope method. You can input your PSA values with dates at:
PSADT Calculator from Memorial Sloan Kettering

PSA Density (PSAD)
PSAD is a calculation of the PSA value divided by the gland volume (in cubic centimeters). A value of 0.1 or greater correlates to previous discussion of the maximum PSA from benign prostatic tissue. The gland volume is normally calculated as part of an ultrasound exam in conjunction with biopsy but a skilled Urologist can make a good guesstimate based on a Digital Rectal Exam.