PSA test: what it measures and when it makes sense

What is PSA and what does the test measure?

The prostate is a walnut-sized gland located just below the bladder. The gland produces fluid that forms part of semen. As men age, the prostate slowly grows; this is normal and proceeds without symptoms in most men.

PSA stands for prostate-specific antigen, a protein produced almost exclusively by prostate cells. Small amounts normally enter the bloodstream. The PSA test measures how high that concentration is at the moment of the blood draw.

Important to know beforehand: the test measures the activity of prostate tissue, not the presence of cancer. Anything that irritates the prostate or makes it grow can influence the value. The result is therefore a clue that needs interpretation, not an answer to the question of whether something serious is going on.

Why PSA can be elevated without cancer

An elevated PSA value often has an innocent explanation. The value can rise due to, among other things:

• benign enlargement of the prostate, which develops in many men as they get older
• inflammation of the prostate or a urinary tract infection
• intensive cycling, ejaculation or a rectal examination shortly before the blood draw
• ageing itself: the value gradually rises with age

The test is therefore sensitive, but not specific: many men with an elevated value turn out to have no cancer on further investigation. A single result is therefore hard to interpret without context.

The reverse also occurs: prostate cancer can exist without the PSA value being elevated. A normal result makes cancer less likely, but does not rule it out completely.

The potential benefit of testing

So why test at all? The main reason is early detection. A small proportion of prostate tumours grows quickly, and it is precisely that group that benefits from timely discovery: treatment before the tumour spreads can improve the outlook.

In addition, a normal result can offer reassurance, and the measurement provides a baseline that a doctor can compare later measurements against. For some men that insight carries real weight: they would rather know where they stand than wait and see.

The downside: overdiagnosis is a real risk

Against that potential benefit stands a real drawback. Most prostate tumours grow so slowly that they would never have caused symptoms during a man's lifetime. A PSA test brings those tumours to light as well, and what has been found is hard to ignore.

An elevated value also often leads to follow-up investigations that ultimately show no cancer, while the uncertainty and burden of that process are very real. And treating a slow-growing tumour can cause side effects, such as erectile problems and incontinence, without it being established that the treatment extends life.

Guidelines therefore do not routinely recommend testing in men without symptoms. That does not mean testing is wrong; it means the choice is yours. Anyone who knows the pros and cons and chooses deliberately is making an informed choice, and that choice turns out differently for one man than for another.

When a test may be worth considering sooner

There are situations in which a PSA test can come into view sooner. With urinary symptoms, the value can help you and a doctor decide whether further investigation is needed, although urinary symptoms more often fit benign enlargement than cancer. At an older age, when prostate cancer is more common, a measurement can also be a deliberate choice.

If prostate cancer runs in your family, that can be a reason to raise the subject actively. That applies especially when several close relatives have had the disease.

What to do with the result

An abnormal value is not a diagnosis, and no reason to panic either. PSA fluctuates naturally, and a temporary rise caused by inflammation or exertion settles by itself. The usual first step is therefore a repeat measurement after a few weeks, at rest and without the factors that can cloud the value.

If the value remains elevated, further investigation follows. It typically proceeds step by step, with an MRI scan first and a tissue biopsy only if there are grounds for one. Only then can it be established with certainty whether cancer is present, and if so, of what type.

At Bloodworks, every result is reviewed by a doctor. If the value is abnormal, the report explains what that may mean.

Practical: rest around the blood draw

PSA is measured with a simple blood draw; you do not need to fast. It is, however, sensible to avoid the following in the days before the draw:

• intensive cycling, especially on a hard saddle
• ejaculation
• a rectal examination

These can temporarily raise the value and cloud the result. If you have recently had a bladder or prostate infection, wait until you have recovered before testing. That way you avoid an unnecessarily worrying result and an unnecessary repeat measurement.

The PSA test can provide valuable information, but it is not a simple yes-or-no test. Whoever measures also chooses the questions a result can raise. That is exactly why it pays to make the decision beforehand, rather than afterwards.

If after weighing things up you choose to test, you can do so at Bloodworks without a referral, with review by a doctor and a personal PDF report.