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What’s Free PSA and How Is It Used to Diagnose Prostate Cancer?

Overview

A free prostate-specific antigen (PSA) test is used to confirm test results from a PSA test. A PSA test is used to see if you may have prostate cancer. The test measures the level of PSA in your blood. If your levels are high, you may have a condition that’s not serious, such as a prostate that’s enlarged or inflamed prostate, or you might have prostate cancer. A free PSA test may be used instead of a biopsy to rule out prostate cancer, though you may still need a biopsy if your free PSA test results indicate a risk of cancer.

Keep reading to learn more about free PSAs and prostate cancer.

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Definition

PSA vs. free PSA

PSA is an enzyme that binds to proteins in semen and breaks them down. This makes the semen more liquid. Semen that’s more liquid can more easily move sperm to a woman’s fallopian tubes during the reproductive process.

PSA is produced mainly in your prostate gland and is released into your semen. During ejaculation, some PSA passes into your bloodstream through the rich blood supply of the prostate. Two types of PSA circulate in your body:

  • Free PSA is PSA that hasn’t bound to any proteins.
  • Bound PSA is PSA that has bound to proteins.

When your PSA is tested, it may be measured two ways:

  • A free PSA test measures only the unbound PSA in your bloodstream.
  • A PSA test measures your total PSA, meaning both your bound and free.
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Purpose

Free PSA test

The free PSA test is sometimes given instead of a biopsy if your PSA levels are slightly elevated. It also may be used to give your doctor an idea of how aggressive the cancer is if your cancer has returned after treatment.

PSA is tested by taking a sample of blood, usually from your arm. The sample will be sent to a laboratory for testing and the results will be given to your doctor.

PSA testing has a number of limitations.

  • The PSA test is known to have a high rate of false positives.
  • It’s not uncommon for a man to have prostate cancer when his PSA is below the limits that indicate there might be cancer.
  • About 75 percent of men who have an elevated PSA do not have cancer.
  • Normal PSA ranges were established primarily on white males, though PSA levels may vary depending on a man’s ethnicity.
  • There can be changes in PSA levels if they’re tested by a different lab or technicians use different testing methods.

PSA levels by age

Following are normal PSA levels by age:

Age Total PSA, normal reference range (ng/mL)
< 50 0.0 – 2.5
50 – 59 0.0 – 3.5
60 – 69 0.0 – 4.5
70 and older 0.0 – 6.5
 

Source: British Columbia Medical Journal

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Results

What do your test results mean?

In general, the higher your PSA level and the lower your free PSA level, the greater your risk of having prostate cancer. Ranges are determined by age. As you get older, your PSA levels will normally rise, even if you don’t have prostate cancer.

Doctors also look at other aspects of PSA, including:

  • PSA velocity. Changes in your PSA levels, called PSA velocity, are another consideration. If your PSA levels rise rapidly, your risk of prostate cancer is greater.
  • Doubling. The faster your PSA doubles, the greater your risk of more aggressive prostate cancer. Doctors also use doubling time to determine if prostate cancer has spread in men who already have been diagnosed with the disease.

Free PSA

Free PSA is measured as the proportion of free PSA to total PSA. Below is a table outlining the likelihood of finding prostate cancer based on the percentage of free PSA in men with a total PSA between 4ng/mL and 10 ng/mL, according to the Journal of American Medical Association.

Percentage of free PSA Probability of prostate cancer
0 –10% 56%
10% –15% 28%
15% –20% 20%
20% –25% 16%
Greater than 25% 8%
 

Factors that affect PSA levels

Changes in PSA levels don’t automatically mean you that have prostate cancer. A number of factors can increase or reduce your levels.

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Free PSA vs. biopsy

Free PSA vs. biopsy

On average, free PSA testing can reduce the need for 20 percent of unnecessary biopsies. It also can help determine if there’s a greater likelihood you have prostate cancer. If your results suggest that you may have prostate cancer, you’ll still need a biopsy to confirm the prostate cancer diagnosis.

When you have a prostate biopsy, a specialist called a urologist will take small samples of tissue from your prostate gland using a special hollow needle. The tissue is examined under a microscope to see if cancer cells are present.

Side effects are common, but rarely serious. You may experience:

  • bleeding from the site of the biopsy
  • blood in your urine or semen
  • trouble urinating

Pros and cons

There are several advantages to having your free PSA tested instead of having a biopsy for elevated levels of total PSA. These include:

  • A prostate biopsy is an invasive procedure that carries a greater risk of infection and complications.
  • Although biopsies are usually performed using local anesthetic, most men find them uncomfortable. Some men report pain.
  • The cost of a biopsy is significantly higher than free PSA tests.

The primary advantages of a biopsy are that if you have cancer, tissue samples taken during the biopsy can provide more information about your condition. A biopsy can provide your doctor with information about the size of the tumor and give your doctor an idea of how aggressive the cancer is. Your doctor can use results from a biopsy to assign a stage and grade for your cancer, which will help you and your doctor decide your best treatment options.

Costs

Unless you have symptoms of prostate cancer or a family history that puts you at greater risk, a free PSA test can be a logical step if your total PSA levels are high. The test may eliminate the need for a biopsy, which is a far more expensive procedure.

Costs for medical services vary from region to region, and even from doctor to doctor. A free PSA test is a simple blood test that usually cost less than 100 dollars. You may have to pay for an office visit, as well. An office visit will almost certainly be more expensive if you see a urologist instead of your primary care doctor.

Even if performed in your urologist’s office rather than an ambulatory care facility, a biopsy will be significantly more expensive. Fees will include:

  • consultation for the urologist
  • ultrasound used to help guide the needle biopsies
  • pathology consultation for reviewing the biopsies
  • miscellaneous supplies
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Outlook

Should you have a free PSA test?

If your total PSA levels are high, it’s often a good next step to have a free PSA test rather than going straight to a biopsy. Ultimately, though, it’s a question that you and your doctor should discuss.

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