PSA stands for Prostate Specific Antigen. It is a produced by the prostate and is not produced anywhere else in the body. Its main function in the body is to keep the ejaculate in a liquid form. An elevated value can suggest that there is an abnormality within the prostate. However it is not diagnostic of prostate cancer.
PSA can be elevated for reasons other than prostate cancer these include
- An increased value is found with age
- A Benign (non cancerous) enlargement of the prostate, commonly known as BPH
- Urine infection
- Prostate infection, known as Prostatitis
- Urinary retention
- Operations (including biopsy) on the prostate
- Ejaculation and cycling can also cause a small rise
To distinguish between an elevated level from prostate cancer and from one of the above causes your doctor can
- Test the urine to rule out infection
- Perform a rectal examination
- Take consecutive levels and look at how fast the PSA is climbing (PSA velocity)
- Compare the value to the size of prostate (PSA density)
- Use age specific values, the following levels are commonly used
Ultimately to diagnose prostate cancer a small sample of the prostate (prostate biopsy) will need to be taken and examined by the pathologist under the microscope. This procedure is usually performed under local anaesthetic (with the patient awake) with an ultrasound probe placed in the back passage, usually around 12 biopsies would be taken. See TRUS and Biopsy.
It is important to stress that a normal level does not rule out prostate cancer completely, it just makes the diagnosis less likely. Conversely a high level does not diagnose prostate cancer, but does make the diagnosis more likely. This is where your doctor or Urologist will help you in understanding what your value means.
Occasionally your specialist may suggest a biopsy if the PSA test is normal i.e. if he/she feels the Prostate feels abnormal on rectal examination.
There is no upper limit for PSA and extremely high levels in the thousands although rare would be diagnostic of prostate cancer.
PSA is a useful test for following up patients after treatment. Following surgical removal of the gland the PSA should drop to 0. If it doesn’t or starts to climb at a later date this potentially could suggest recurrent disease. Here your Urologist or Oncologist would advise.
PSA is also used for managing patients with benign prostatic enlargement and can be used to help predict those men that may need more aggressive treatment (although it is not a mandatory test for this area). Again your doctor will advise you if its being used for BPH rather than for the diagnosis of prostate cancer.