What is the difference between PSA and free PSA?

What is the difference between PSA and free PSA? Do I need to have both tests?

Whether you need both tests really depends on your individual situation. That’s why this question generates so much debate and confusion.

PSA, a protein produced by prostate gland cells, circulates through the body in two ways: either bound to other proteins or on its own. PSA traveling alone is called free PSA. The free-PSA test measures the percentage of unbound PSA; the PSA test measures the total of both free and bound PSA.

Prostate cancer can raise PSA levels, but so can other conditions. These include an enlarged prostate, prostatitis, and advancing age. In fact, studies have shown that about 75% of men with an elevated PSA do not have prostate cancer. To determine which men actually have cancer and which don’t, physicians traditionally perform a biopsy. Undergoing a biopsy isn’t as traumatic as surgery, but it does cause discomfort and can provoke anxiety.

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. Studies have shown that men with a total PSA in this “gray area” and a free PSA greater than 25% are more likely to have a benign condition than to have cancer, making a biopsy unnecessary. Men with a total PSA in the same range and a free PSA below 10% need to have a biopsy. More likely than not, they have prostate cancer (see table below).

In some cases, men with a “normal” PSA actually have cancer, but that low PSA doesn’t prompt a biopsy. A low PSA and a low percentage of free PSA, however, probably would. That’s why some doctors automatically order both tests at the same time. I tend to order a free-PSA test when a total PSA yields borderline results and when the PSA seems to be rising quickly, even if the actual number is relatively low. So, while the free-PSA test isn’t essential, the results may sway your decision on whether to have a biopsy when combined with other tests. In the future, other tests may help determine whether changes in PSA are driven by cancerous tissue or benign causes.

Probability of finding prostate cancer based on % free PSA in men with a total PSA between 4 ng/ml and 10 ng/ml

% free PSA Probability of prostate cancer
0%–10% 56%
10%–15% 28%
15%–20% 20%
20%–25% 16%
Greater than 25% 8%
SOURCE: Journal of the American Medical Association, May 20, 1998.

Originally published April 2009; last reviewed March 21, 2011.

Comments
9
Karl Isabelle

I am a man of 66 yrs old. I just had a Total PSA & a Free PSA test. The result has shown the following:
T-PSA Result is 73.50
F-PSA Result is 5.15

As I am a bit confused about this result so I would like to have your advice if I have a risk of a prostate cancer.

Grateful to give me your opinion about this result.

Waiting on your prompt reply.

Thanks,
Karl

Jagdish

I am a man of 55 years old , I just had a total PSA & free PSA test , the result is as follows:
Total PSA is 3.232ng/ml.
Free PSA is 0.845 ng/ml.
Please advise me if i have a risk of prosate cancer.
Thanks in advance , looking forward your opinion,
Thank you,

Ron Adair

I have a total PSA of 5.3, and a free PSA of .34, and a Percent Free PSA of 6.04. Can you advise me of the risk factor?

Thank you very much,

RA

Robert Kocher

I have been having prostate and PSA exams since 2003. My PSA on the first exam was 4.2. The doctor did 12 biopsies found nothing and was diagnosed as acute prostatitis. I was given Levaquin for 10 days and started three month follow-up exams. The PSA went down to 3.1 in 12/2004 then spiked to 7.4 in June 2005. August 2005 more biopsies, found nothing diagnosis chronic inflammation and was given Cipro for 10 days. Resulting PSA went down to 3.4 by 11/2006 and was 6.3 in 12/2010. PSA then went to 6.8 in 08/2011. More biopsies, no malignancies again. PSA last test 06/2014 was at 6.9 up from 5.8 in January 0f 2014 and free PSA at 10% down from 11%. Doctor wants to do biopsies. I am inclined to ask for a prescription for 10 days and then have the PSA redone again in September. What is your opinion. I will be 67 in November. My father lived to 82 years and died of bone cancer.

Mark

I am a 48 year old man. My PSA has been fluctuating over the past four months from 6.8 to 4.2 to 3.6 to 4.6. However, each of the four times I have been tested my “free PSA” has been 0. (Yes, zero). I have been to two nationally recognized prostate cancer centers in southeast Michigan, but no one has ever seen a consistent “free PSA” of 0. I have a biopsy scheduled in 2 weeks.

Any thoughts you may have would be appreciated.

Thanks,
Mark

Richard

I am 72 years old and have been diagnosed with andenocarcinoma in one lobe of the prostate. The size of the tumor is 1.2mm with a gleason score of 6. I also have an enlarged prostate that has weakened my urine flow. This has improved after the Urologist put me on Lucrin hormone treatment for six months. I am on my second dose. I just had my PSA done and the total PSA is 2.35 with free PSA at 1.01 and a percentage of free PSA at 42.9. This high percentage is of great concern to me. Could the high percentage be as a result of the Lucrin hormone theraphy. My testosterone from Lab result is 0.20
Can you please give me your thoughts on the above. Thank you. Richard

Samuel Tso

I am a 65 years old man.

I had my first PSA tested in Jun 2008 and the results were Total PSA: 5.8 ng/ml and Free PSA:1.17 ng/ml. U/S prostate (transretal) followed by Trus Guided Prostate Biopsy were performed within two weeks from PSA test. U/S showed enlarged Prostate gland measurement 6.1×3.4×4.1 cm (TDxAPxCC). There was mainly hypertrophy of the central zone, suggesting benign prostatic hyperplasia. No focal lesin is seen in the peipheral zone. The contour of the prostat gland appears smooth. Biopsy of the protstae gland was perfomred and the procedure was unremarkable.

More than ten PSA tests were conducted from 2008 to end 2012 the Free PSA fluctuated from 5.7 to 7.8 and Free PSA from 0.98 to 1.41. In Aug 2013 PSA went up to 8.48 and in Jun 2014 PSA went up to 9.59, the doctor suggests to peerform a Biopsy. I am very concerned to do another Biopsy and would be grateful to have your advice by return.

Thanks a lot.

Sam
10 Aug 2014

Howard Himelstein

I have just been diagnosed with Pca…My Gleason is a 3+3=6, T1c, Total PSA is .65, psad is .01, but my free psa is .11 and my PSA3 test is 58.4…I read in Patrick Walsh’s book that if you have a free PSA under 15, there is an almost certain chance that one’s cancer is the aggressive type. When I asked my doctors about that they told me not to be concerned as it doesn’t apply to my situation. Does anybody know why it doesn’t? Can’t seem to get a solid answer from my uros…

PS – just had an Onotype DX test and it came back at a good and low 15.

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