PSA

What is being analysed?
This test measures the level of PSA in the blood. PSA is a protein produced by the cells of the prostate and is a marker of prostate cancer. It can be measured in all males, and high levels can be caused by prostatitis (inflammation of the prostate), benign prostatic hyperplasia or prostate cancer.
PSA is present in the blood in two forms: free (unbound) and complexed (bound to a protein). Total PSA testing therefore measures both the free form and the form bound to other plasma proteins, while free PSA testing measures the percentage of circulating PSA that is not bound to proteins.
Measuring both forms (free/total PSA ratio) can help distinguish between cancerous and non-cancerous conditions. Patients with prostate cancer often have an altered ratio of the two forms of PSA, in particular low levels of free PSA and increased levels of the bound form.

How is the sample collected for testing?
The blood sample is obtained by drawing blood from a vein. In the two days before the test, it is important to avoid ejaculation and strenuous physical activity that could affect the prostate, such as cycling. The blood should also be drawn before any rectal examination or prostate biopsy.

How is it used?
When is it requested?
What does the test result mean?
Is there anything else I should know?

How is it used?
PSA testing helps diagnose prostate cancer and monitor the response to treatment in patients with prostate cancer

When is it requested?
PSA testing is not recommended as a screening test for prostate cancer, because in many cases it detects, at an early stage, tumours that grow extremely slowly and are biologically not very aggressive, leading to unnecessary further tests and treatment.
However, the American Cancer Society recommends PSA testing and a rectal examination for all men over 50, for those with a family history of prostate cancer and for those at increased risk of prostate cancer, such as African American and African Caribbean men, starting at age 40-45. It also recommends that patients be informed about what the test means and about its advantages and disadvantages before it is carried out.
The same tests should also be requested when there are symptoms such as difficult, painful and/or frequent urination, or back and/or pelvic pain. As well as prostate cancer, these symptoms may be caused by infection and prostatitis, and in these cases a urine culture is recommended. These conditions can cause temporary increases in PSA levels, which should be rechecked after a few weeks to confirm that they have returned to normal.

Free PSA is requested when the total PSA level is moderately raised, to distinguish prostate cancer from benign prostatic hyperplasia. PSA testing may be requested together with other investigations, such as a rectal examination or a biopsy, to confirm a diagnosis of prostate cancer. Once the diagnosis has been made, PSA levels can be used to monitor the patient’s response to treatment.

What does the test result mean?
The normal total PSA value is below 4.0 nanograms (ng) per millilitre (mL) of blood. PSA levels above 10.0 ng/mL may indicate a high probability of prostate cancer. Levels between 4.0 ng/mL and 10.0 ng/mL are suggestive of benign prostatic hyperplasia, a non-cancerous condition of the prostate that is common in older men. Raised total PSA levels may also indicate a prostate infection. Finally, they may indicate prostate cancer, mostly confined to the gland.
Free PSA, expressed as a percentage of total PSA, can help predict the likelihood of prostate cancer, particularly in patients with total PSA levels between 4.0 ng/mL and 10.0 ng/mL, the so-called grey zone. Free PSA testing may also be useful in the early diagnosis of cancer when PSA values are between 2.5 ng/mL and 4.0 ng/mL.
A free PSA percentage above 25% suggests a low risk of cancer, while a lower percentage suggests a higher probability of prostate cancer. This percentage can help reduce the number of unnecessary biopsies. A recent study also suggests that a very low free-to-total PSA ratio (below 14%) may be associated with a more aggressive form.

In many cases, test results are reported as numbers rather than with words such as “high” or “low”, “positive” or “negative”, or “normal”. To interpret laboratory results correctly, you need to know the reference range. However, reference range values depend on many factors, including the patient’s age, sex, medicines taken, circadian rhythm and fasting status, as well as the method and instrument used by the laboratory.

During treatment for prostate cancer, PSA levels should fall, and by the end of treatment they should be very low or undetectable; otherwise the treatment has not been effective. After treatment, periodic PSA measurements detect any recurrence. Because even small increases in PSA can be significant, the test should be carried out by the same laboratory to minimise analytical variability.

Is there anything else I should know?
A prostate biopsy or prostate surgery can significantly increase PSA levels. Blood should therefore be drawn before the procedure or six weeks after it.
Strenuous physical activity such as cycling, or ejaculation, can temporarily increase PSA levels. High doses of certain chemotherapy drugs, such as cyclophosphamide and methotrexate, can increase or decrease PSA levels.

1. What is done in the case of prostate cancer?
2. Does the PSA test detect all prostate cancers?

1. What is done in the case of prostate cancer?
The most common treatments include radiotherapy, surgery and hormone therapy.

2. Does the PSA test detect all prostate cancers?
No. Sometimes cancer cells do not produce PSA, and the test result will be negative even though cancer is present. In addition, about 20% of tumours show no rise in PSA in the early stages of the disease.