The PSA is never meant to be a one-shot reading; it’s not a constant number, forever set in stone like the Ten Commandments.  Instead, it’s more like a Polaroid snapshot – a quick capture of one moment in time.  PSA fluctuates; that’s why it’s good to follow the general trend of the number over time, instead of just looking at one reading and saying with absolute confidence that a man definitely does or does not have prostate cancer.

That said, if you’re getting a PSA test, let’s make sure it’s as accurate as possible.  Here are some things that can artificially raise or lower your PSA.  A couple of these can be avoided; as for the rest, be sure to tell your doctor.

Don’t get your PSA tested if you have a urinary tract infection.  “This will cause your PSA level to be elevated,” says New York University urologist Stacy Loeb, M.D.  “Urinary retention (when you cannot urinate) will also cause an elevation in PSA.”

Don’t ejaculate for at least two days before you get the PSA test.  This can send more PSA into the bloodstream and can artificially raise your PSA level.

Don’t get the PSA test after your rectal exam.  Your doctor should know this, but sometimes it happens.  The rectal exam, which stimulates the prostate, can also cause PSA to be released into the bloodstream.  This is an avoidable cause of unnecessary worry!

Don’t work out right before your PSA test. Vigorous exercise can cause a “bump” in PSA, with bicycle riding being the biggest culprit.

Do tell your doctor if:

You are taking Proscar or Avodart for BPH (benign prostate enlargement), or Propecia for hair loss.  All three of these drugs can throw off your PSA level, making it seem lower than it actually is.  “To correct for this, if you have been on one of these drugs for two years, your PSA level should be multiplied by 2.0,” says Johns Hopkins urologist Patrick C. Walsh, M.D., co-author of Patrick C. Walsh’s Guide to Surviving Prostate Cancer.  “Then for the next five years, it should be multiplied by 2.3, and after seven years, by 2.5.  Fortunately, these drugs do not affect   measurements.”

You have had surgery for BPH.  A transurethral resection (TUR) or laser procedure for BPH can make your PSA much lower, because there isn’t as much tissue inside the prostate as there used to be.  This, too, can give a false impression that everything’s okay, when it might not be.

You have had recent manipulation of the urinary tract.  “Catheter placement and other procedures in the urinary tract could cause the PSA level to go up and give a false impression,” says Loeb.  Vigorous bicycle riding is the biggest culprit of a PSA “bump.”

You have liver problems.  Liver cirrhosis can lower PSA, and so can liver fibrosis (scar tissue in the liver, which develops as the liver attempts to fix cells damaged by disease). “If you have a liver disease, talk to your doctor about how it might affect the PSA, and if you are a Baby Boomer (born between 1945 and 1965), consider a one-time check for hepatitis C virus infection,” says Johns Hopkins epidemiologist Elizabeth Platz, Sc.D., M.P.H.

The safest bet, says Walsh, is this:  “If your PSA begins to increase steadily, even if this increase is very small, you should see a urologist.”

What if my PSA is significantly higher?  First of all, don’t panic, says Walsh.  “Repeat the test in the same laboratory; in 25 percent of men who have this experience, the reading will be back down to its former level.”

Using the same laboratory is essential, because not all labs use the same assay to measure PSA, and the results can vary slightly.

In another study, New York University urologist Stacy Loeb, M.D., and colleagues tested the same blood sample using two different PSA assays.  “We found a 17-percent difference in the average PSA level,” she says.  “If you got back-to-back PSA tests at two different labs and they were markedly different, you might easily think something important was going on, when in fact there was no change.”

Janet Farrar Worthington
Janet Farrar Worthington is an award-winning science writer and has written and edited numerous health publications and contributed to several other medical books. In addition to writing on medicine, Janet also writes about her family, her former life on a farm in Virginia, her desire to own more chickens, and whichever dog is eyeing the dinner dish.