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Prostate-specific antigen — a protein made by the prostate gland. Small amounts in the blood are normal. Levels can rise for several reasons, which is why PSA is a starting point for a conversation with a doctor rather than an answer in itself.

Whether the PSA in your blood is above 4 ng/mL. It gives a positive or negative result, not an exact number. In some cases, levels between 3 and 3.9 ng/mL can also read positive.

Yes. The test is designed for the person taking it to do at home, following the instructions. For a lot of men, a simple test in hand is an easier way into a conversation they've been putting off.

Some activities can raise PSA for a while and cause a false positive. Wait 24 hours after a long bike or motorbike ride, 24–48 hours after sex or ejaculation, 2–3 days after a urinary catheter or a transrectal ultrasound, and a week after a urinary tract infection.

No. A positive means your PSA is above 4 ng/mL. That can happen with an enlarged prostate, inflammation or infection, as well as cancer, and this test can't tell which. PSA is a prostate marker, not a cancer test. Take your result to a doctor, who will decide what happens next.

Your PSA is in the normal range. A negative result doesn't rule out every prostate condition, so if you have urinary symptoms, talk to your doctor anyway.

In a clinical study of 209 people, it correctly identified 97.2% of samples with raised PSA (sensitivity) and 87.1% of samples without it (specificity), for 92.3% overall accuracy. Put simply: it rarely misses a raised level, but about 13 in 100 samples below the cutoff can still read positive. That's one more reason a positive result goes to a doctor.

It isn't recommended if you take anticoagulant medication or have haemophilia.

Men over 45 without symptoms who want to check their prostate marker, and men with urinary symptoms such as difficulty urinating, pain or needing to go more often. If you have symptoms, see your doctor too, whatever your result.

Read it 5 minutes after you finish the steps. A result read 10 minutes or more later isn't reliable.

No. Any visible Test (T) line alongside the Control (C) line is a positive result, however faint.

The cassette touching other liquids before use, spilling some of the diluent, not collecting enough blood, or adding the wrong number of diluent drops (the test uses 2). Following each step closely is what makes the result reliable.

A test cassette, a dropper vial of diluent, a pipette for collecting blood, two sterile lancets (the second is a spare), an alcohol pad and instructions. You'll also want cotton wool and a timer.

The test didn't work, so there's no result to read. Repeat it with a new test and a fresh blood sample.