The test is particularly used to [1] detect cancer and [2] to assess the response to treatment.  Any man with a PSA above this age adjusted range may well wish to be transferred to a specialist Urologist as there is a risk he could have cancer although there are other causes of a raised blood PSA:-

• infections
• recent prostate biopsies
• having a urinary catheter in (a tube to drain urine)
• prostate or bladder surgery
• prolonged exercise, such as long-distance running or cycling
• ejaculation
• some drugs

There are ways to make the PSA more reliable, if needed:-

Free versus bound PSA

The PSA circulates in the blood in two forms - the free form and the form bound to a protein. Some laboratory, as well as an absolute level provide the ratio of free versus bound. The benign condtions which elevate the PSA mentioned above produce more free form whilst cancer produces more bound form. Therefore, the greater the ratio (ie more free form) to more likely that it is benign (not cancer)

The PSA doubling time (PSA velocity)

This is the time it take the the blood PSA to double. In many cases it hasn't actually doubled but the potential doubling time can be estimated by the following calculation:-

PSA_a                x      t

                        PSA_b - PSA_a

 

Where PSA_a is the first value PSA_b is the second value and t is the time between them. (E.G a PSA increases from 2 to 3 over 3 months the PSAdt = 2/1 x 3 = 6 months). The PSAdt is much more accurate and sensitive to progression and prognosis that a single value. For example, a trial published by Fowler in 1995 showed that if the PSADT was < 10 months, there is a high probability of metastatic disease.