PSA testing is one of the few areas of medicine where the test is simple and the interpretation is not. Men are frequently handed a result with a number on it and very little context, and the number alone rarely settles anything.
What PSA actually is
Prostate specific antigen is a protein made by the prostate gland. Small amounts leak into the bloodstream normally, which is why everyone with a prostate has a measurable level.
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.
What raises PSA besides cancer
This is where most of the confusion comes from. Levels rise with:
- Benign enlargement of the prostate, which is extremely common with age
- Infection or inflammation of the prostate, which can push levels up sharply and take weeks to settle
- A urinary tract infection
- Recent catheterisation, cystoscopy or prostate biopsy
- Ejaculation within the previous couple of days
- Long distance cycling in the days before the test
The practical consequence is that timing matters. A test taken shortly after an infection, or the morning after a long ride, can produce a result that causes needless alarm. Where a raised level turns up unexpectedly, repeating it after a few weeks is often the sensible next step rather than proceeding straight to a biopsy.
Why there is no single normal value
Thresholds around 4 nanograms per millilitre get quoted often, and they are more of a rough guide than a rule.
PSA rises naturally with age, so a level that would be unremarkable at seventy could be worth investigating at fifty. Prostate size matters too, since a large benign gland produces more PSA simply by having more tissue. And the direction of travel is often more informative than any single figure, which is why a level that has climbed steadily across three annual tests is taken more seriously than one that has sat still for years, even at a higher value.
This is also why a low PSA is reassuring rather than conclusive. A minority of aggressive prostate cancers produce relatively little PSA, which is why the digital rectal examination remains part of the assessment.
What happens after a raised result
The pathway has changed considerably, and for the better.
It used to be that a raised PSA led fairly directly to a biopsy. Now, in most cases, an MRI scan of the prostate comes first. The scan identifies areas that look suspicious and grades how concerning they are. If the scan is clear and other factors are reassuring, a biopsy can often be avoided entirely. If the scan shows something, the biopsy is targeted at that specific area rather than sampling blindly.
That change means fewer men have biopsies they did not need, and the biopsies that do happen are more accurate.
Deciding whether to test at all
This deserves more discussion than it usually receives.
Testing has a real benefit, which is finding aggressive cancer early enough to cure it. It also has a real cost, which is finding slow growing cancer that would never have caused harm, and then facing decisions about treatment that carries its own side effects.
A reasonable position is that men from around fifty should have the conversation, and men with a family history of prostate cancer, or of African ancestry, should have it earlier, from around forty five.
The part that matters is understanding beforehand what a raised result would lead to. Anyone having the test should know that in advance rather than finding out afterwards.
The short version
PSA is a piece of information, not a verdict. Interpret it alongside your age, your prostate size, your previous readings and an examination. If it is raised, an MRI usually comes before any biopsy. And decide whether you want the test before it is taken rather than after.