Prostate-Specific Antigen (PSA)
If you have symptoms of prostate disease, such as difficulty in passing urine, straining or taking long time while urinating, hesitancy, weak flow, terminal dribbling or passing urine more frequently than usual especially during the night.
A blood sample taken from a vein in the arm at any time of the day
Avoid ejaculation for 48 hours before sample collection as this has been associated with elevated prostate specific antigen (PSA) levels; the sample should also be collected prior to your healthcare professional performing a digital rectal exam (DRE) and prior to or 6 weeks after a prostate biopsy. PSA may remain high for many months following a urinary tract infection, and for 48 hours following vigorous exercise, especially riding a bicycle).
Blood is being tested for the amount of PSA it contains. PSA is a protein produced mainly by cells in the prostate gland and can be a useful indicator of prostate cancer. This protein can be found in all males; however, men whose levels are increased may have an infection of the prostate gland (prostatitis), prostate enlargement or prostate cancer. In blood, PSA is present both as free PSA and as complexed PSA bound to other blood proteins. The free PSA test measures the percentage of the total PSA that is not bound to proteins in the patient’s blood.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm. You are likely to be advised to avoid ejaculation and vigorous physical activity affecting the prostate, such as bicycle riding, during the two days before the blood test. A blood sample should not be taken until at least a week after a digital rectal examination.
Is any test preparation needed to ensure the quality of the sample?
Avoid ejaculation for 48 hours before sample collection as it has been associated with elevated PSA levels; the sample should also be collected prior to your healthcare professional performing a digital rectal exam (DRE) and prior to or 6 weeks after a prostate biopsy, as both of these can also elevate PSA levels. Men should not have exercised vigorously in the previous 48 hours and also should not have an active urinary infection at the time of blood collection.
How is it used?
When is it requested?
Using the PSA test to screen healthy men for prostate cancer is not recommended at present in the UK. Currently there is no evidence to show that the overall benefits of a PSA- based screening programme outweighs the risks. PSA is still a poor test for prostate cancer detection (low specificity) and it has led to harm of over-diagnosis and over-treatment in up to 50 % of men. A PSA test does not distinguish a slow-growing cancer from a fast-growing cancer.
Risk factors for prostate cancer include;
- Increasing age
- Black ethnicity
- Family history of prostate cancer
- Being overweight or obese (especially in advanced prostate cancer)
Your healthcare professional will take these risk factors into account to give you the best available information and support your decision.
The Public Health England website has a guidance document on Prostate Cancer Risk Management Programme (PCRMP). It includes a summary sheet on advice for well men aged 50 and over.
Two other PSA tests are also available and may be requested; ratio of free to total PSA (f/t PSA) or complex PSA (cPSA). These tests may improve the specificity and reduce the number of unnecessary biopsies. It is helpful when patient’s total PSA value < 10 µg/L (which is known as the diagnostic “grey zone”) with negative DRE It may distinguish between prostate cancer and other non-cancerous conditions such as benign prostatic hypertrophy (BPH). Studies suggest that using these PSA isoforms in men who fall into this grey zone could potentially reduce over diagnosis and maintain a high cancer detection rate.
What does the test result mean?
The 'normal' value for total PSA varies with age and is generally considered to be less than 3.0 micrograms (µg) per litre (L) in men aged 50-69 years. Recent literature shows that age-specific PSA cut-offs for detecting prostate cancer is highly variable. It may differ with patient’s demographics and clinical characteristics.
A high serum PSA result >3 µg/L alone does not automatically lead to other investigations e.g; prostate biopsy. There are several other factors to be considered; such as prostate size, digital rectal examination (DRE) findings, age, ethnicity, family history of prostate cancer, body weight, co-morbidities, history of any previous negative biopsy or any previous PSA history. Your healthcare professional may consider these factors along with raised PSA (> 3 ng/mL) result when referring patients to specialist care.
Total PSA level greater than 10.0 µg/L may indicate a high probability of prostate cancer. Results between 2.0 µg/L and 10.0 µg/L may be due to BPH, a non-cancerous swelling of the prostate that occurs most frequently in older men. Increased total PSA levels may also indicate a condition called prostatitis, which is caused by an infection.
There is some evidence that the free PSA ratio (the percentage of total PSA not bound to proteins) can help predict the probability of cancer, especially in patients with total PSA levels in the 'grey-area’ range of 2.0 to 10.0 µg/L. A free-PSA test result above 25% is thought to suggest a lower risk of cancer, whereas a lower percentage suggests a higher probability of disease. This ratio may help reduce the number of unnecessary biopsies. In most cases, test results are reported as numbers rather than as "high" or "low", "positive" or "negative", or "normal". In order for the doctor to understand laboratory results it is necessary for them to know what the reference range (or ‘normal value’ range) is for the laboratory where the test is performed. Reference ranges can be influenced by the test method and instrument used by laboratory. To learn more about reference ranges, please read the article, Reference Ranges and What They Mean.
Is there anything else I should know?
Prostate biopsy or operations on the prostate will significantly elevate PSA levels. A blood test for PSA measurement must be performed before surgery or six weeks after.
Ejaculation and vigorous physical activity affecting the prostate, such as bicycle riding, may cause a temporary rise in PSA. A blood sample should be taken either before a digital rectal examination as pressure on the gland during the examination will lead to an increase in the PSA value or alternatively after at least a week after the examination. Some chemotherapeutic drugs, such as cyclophosphamide, methotrexate, and also other medications such as aspirin, statins, diuretics, finasteride, and dutasteride may affect PSA results.
If I have prostate cancer, what are my options?
Are the recommendations for PSA testing different for different ethnic groups, such as those of Afro-Caribbean descent?
Will PSA testing detect all prostate cancers?
I have heard my doctor use the terms PSA Density, PSA Velocity, PSA Doubling Time. Please explain what these are.
PSA Density refers to the relationship of the PSA level to the size of the prostate measured by ultrasound examination. Men with larger prostates tend to produce more PSA, and so men with a benign enlarged prostate (BPH) can have higher 'normal' PSA levels. Men with a PSA value in the 2 µg/L to 10 µg/L range but with an enlarged prostate gland have a lower probability of prostate cancer than those with a small gland.
PSA Velocity refers to how quickly PSA results change over time. There is evidence to indicate that the development of prostate cancer requiring treatment is associated with a faster increase in the PSA value over time.
None of the above is routinely implicated in clinical practice in detecting prostate cancer.
PSA Doubling Time is the time it takes for the PSA value to double. This may be useful in following treatment and determining the type of treatment.
Elsewhere On The Web
Prostate Cancer UK: Prostate Cancer Tests
ACB, NICE Guidline Summary QS91: Prostate Cancer
NICE Guidline QS91
NHS Cancer Screening Programmes: Prostate Cancer Risk Management
Macmillan cancer support
Public Health England; Prostate cancer risk management programme (PCRMP): benefits and risks of PSA testing