The PSA test for prostate cancer is surprisingly controversial. Many experts, in fact, now recommend against the test for most men, saying that the cancers it detects are often relatively harmless tumors that would never progress beyond the gland, and that treatment, usually with surgery or radiation, can be more dangerous and debilitating than the disease itself.

Still, many men concerned about cancer still opt for the PSA test. And some men already diagnosed with the cancer need periodic tests to track the progress of the disease.

In those cases, it's important to make sure that the test is as accurate as possible. Here's what you need to do.

How to Prepare for the Test

The PSA test is meant to check for prostate cancer by measuring the prostate-­specific antigen (PSA), a protein often elevated in men with prostate cancer.

But only about 25 percent of men with mild and moderate elevations might actually have prostate cancer. Instead, those high levels could be due to problems such as an enlarged prostate gland (which occurs with aging), a prostate infection, recent sexual activity, or even a recent long bike ride, says Scott Eggener, M.D., co-­director of the prostate cancer program at the University of Chicago.

These steps can make sure that the results are as accurate as possible:

Wait after a urinary tract infection. If you’ve had a recent UTI or catheter, hold off on the test for a few months. Both can cause prostate inflammation that can artificially elevate PSA levels.

Abstain from sex. Ejaculation up to 72 hours before the test could raise PSA levels a minimal amount.

Have the digital rectal exam after the blood test. As part of a prostate-cancer exam, your doctor may perform this test, which is used to check the size of the prostate gland and to look for abnormal bumps or other changes. But if you do it before having the PSA test, it could cause the release of PSA into the bloodstream and possibly lead to a false positive result.

Repeat if results are high. “PSAs are notorious for bouncing around a lot, and they can even fluctuate by as much as 10 to 20 percent depending on the assay that’s used in the laboratory,” Eggener says. So wait about four to eight weeks to get retested.