PSA total and free PSA: what the numbers actually mean

Few numbers worry men as much as a PSA result, and few are as widely misread. A raised figure is not a diagnosis, and a normal one is not a guarantee. Here is what the test actually measures, and what the two numbers on the report mean.

What PSA is

PSA stands for prostate specific antigen. It is a protein made by the prostate, and its job has nothing to do with disease: it thins the semen so sperm can move. Small amounts leak into the bloodstream, and that is what the test picks up.

The important word is prostate specific — not cancer specific. PSA tells you the prostate is producing more protein than usual. It does not tell you why.

Why the number goes up

Plenty of ordinary things raise PSA, and most of them are not cancer:

• Benign enlargement. A bigger prostate simply has more tissue making PSA. This is the most common reason for a raised reading in men over 50.
• Inflammation or infection. Prostatitis can push the number up sharply, sometimes into ranges that look alarming, and it comes back down once the inflammation settles.
• Recent ejaculation. Enough to shift the result. Most guidance suggests abstaining for a couple of days before the test.
• Cycling and other pressure on the perineum. A long ride shortly before the blood draw can nudge the figure.
• A digital rectal examination or a catheter, if done shortly before the sample.
• Age. PSA drifts upward through life in men with entirely healthy prostates.

And it can go the other way: some medicines taken for benign enlargement roughly halve PSA. If you take one, your doctor needs to know, because an apparently reassuring number may be masking a higher true value.

Total PSA and free PSA

PSA travels in the blood in two states. Most of it is bound to other proteins. A smaller part circulates unattached — that is the free fraction.

Total PSA is everything together. Free PSA is the unbound part, usually reported as a percentage of the total.

The reason anyone bothers with the split is that the proportion tends to differ by cause. Benign enlargement is generally associated with a higher percentage of free PSA; cancer tends to be associated with a lower one. So when the total sits in the ambiguous middle ground, the ratio gives the urologist a second piece of information before deciding whether a biopsy is warranted.

It is a tendency, not a rule. The ratio shifts the odds; it does not settle the question by itself.

How to read your own result sensibly

One reading means little. The trend over time — how fast the number is moving — carries more information than any single value.

Compare like with like. Different laboratories use different assays and their results are not always interchangeable. Where you can, stay with the same lab.

Context decides. Your age, the size of your prostate, your symptoms, your family history and the examination all feed into what the number means. That is the urologist's job, and it is the reason a result should be interpreted in the clinic rather than at the kitchen table.

If your PSA comes back raised

Do not panic, and do not ignore it. Both reactions cost you. The usual sensible path is to repeat the test after a period, avoiding the things that artificially raise it, and to see a urologist who can put the figure alongside everything else known about you.

The men who do best with prostate problems are not the ones with the lowest numbers. They are the ones who kept testing, kept their appointments, and found out early where they stood.

This article is general information about a common test. It is not medical advice, and it cannot replace an assessment by your doctor.