Prostate specific antigen (PSA)

A high PSA can be caused by a number of conditions affecting the prostate, such as prostate cancer, benign prostatic hypertrophy (BPH, where the prostate enlarges in non-cancerous growth) and prostatitis (where the prostate is inflamed, usually from an infection). Three out of every 4 men who get a positive PSA test do not have prostate cancer.

A urine infection can raise the PSA, so you’ll need to treat the infection first and then repeat the PSA after 6 weeks. Before your PSA test you should avoid vigorous exercise and ejaculation for 48 hours. You should also avoid anal stimulation for a week before the test. This includes sex or sex toys, and if your doctor has performed an intimate examination via the back passage to check the prostate.

If you’ve had any surgery to the bladder or prostate, a urinary catheter or a biopsy of the prostate, you will be advised to wait 6 weeks before having a PSA test.

It is important to note that medications called 5-alpha-reductase inhibitors such as finasteride or dutasteride, which help reduce the size of the prostate in BPH, can lower your PSA level and give you an incorrect result (a false negative).

Prostate cancer does not always cause the PSA level to rise – it will miss prostate cancer in nearly 1 in 7 men, because of a false negative.

The PSA test is not black-and-white - it's a test that if your level is high, it means you need further investigations. Many men with a raised PSA level don't have prostate cancer. This is called a false positive.

A normal PSA level does not rule out prostate cancer – if you have suspicious symptoms, this may warrant further investigations even with this so-called false negative.

Your doctor will ask about your symptoms, particularly in relation to passing urine, and about family history of prostate cancer or BPH. They will consider other risk factors, such as it you are African or Caribbean, obese or aged over 50 – all these can increase your risk of prostate cancer.

They will offer an intimate examination of your back passage, to feel the surface and size of your prostate. This gives further information into the cause of a high PSA or any symptoms.

It can be a difficult decision because there is so much to consider and weigh up. These questions may help you make the decision:

• Am I at increased risk of having prostate cancer? (If you are an older man, especially over 50, if you are Black, or if prostate cancer runs in your family)

• Will I accept further investigations if my PSA is high?

• Will a normal PSA reassure me?

• If I was diagnosed with slow-growing prostate cancer that might never cause any problems, would I still want to have treatment, even though it could cause side effects? Or would I be comfortable having my cancer monitored instead?

If you are over 50, you can ask your doctor for a PSA blood test so long as you understand the risks and benefits.

It's a very personal decision whether to request the test or not, and if you still feel confused, you could talk all this through with your GP.