Q. Do I have to have one of those “finger tests”?
A. No. You simply need to have a PSA test, which is a simple blood test arranged for you by your doctor. It can be done in conjunction with other blood tests.
If your PSA level is abnormal or if your doctor wants to check for the presence of another common cancer (rectal cancer) it would then be suggested that you have a digital rectal examination.
Prostate Specific Antigen:
PSA or prostate specific antigen is a protein produced by the prostate gland. This chemical has an important role in human reproduction. As well as providing nourishment for sperm it aids sperm movement.
A small amount of PSA leaks out into the bloodstream, normally, and can be detected by a specific blood test called a PSA test.
The PSA test
The prostate specific antigen (PSA) test involves taking a small sample of blood, from the vein in the arm, much the same as for cholesterol or glucose tests, and sending it for laboratory testing.
Most of the PSA produced stays in the prostate and only a small amount is found in the blood stream. If the prostate is producing a lot more PSA then more escapes into the blood stream.
The important message is that PSA levels do generally correlate with the risk of prostate cancer, as well as, the risk of aggressive prostate cancer. “A PSA (test) performed once a year provides information about the rate of change which, in practice, is very helpful. A single raised PSA should be double checked (with no ejaculating 48 hours before the test “
How well does the PSA test work for finding prostate cancer?
About 1 in 3 men with a PSA between 4 and 10 ng/ml could have prostate cancer, although this proportion varies with the population tested.
Recent studies have shown that there is still a small risk of prostate cancer, even if blood PSA levels are normal for age. Therefore even a normal blood PSA level does not mean that there is definitely no prostate cancer present.
The only definite way to confirm whether prostate cancer is present or not is by prostate biopsy.
How often should I have a PSA blood test?
The current suggested rate for testing is:
- for men over 50, without any family history of prostate cancer, every 2-3 years
- if PSA levels are at the safe upper limit then consider annual testing
- if you are 40 and have a family history of prostate cancer annual testing is recommended.
Frequency of testing will be more accurately answered after the European (ERSPC) & American (PLCO) screening trials data are published in 2008.
The whole idea is to ensure that should you ever suffer from prostate cancer, you get your diagnosis early, so that your chances of a cure are high.
A ‘normal’ PSA level
As men get older, their PSA levels tend to increase. Because of age related changes, as well as individual differences, there is no firm number that would indicate a definite absence or presence of prostate cancer.
As a general rule, the higher the PSA reading, the more likely it is due to prostate cancer, and that the cancer is aggressive.
Table 1 suggested upper limits of PSA for different age groups
| Ages(years) | Serum PAS(ng/ml) |
| 40-49 | < 2.5 |
| 50-59 | < 3.5 |
| 60-69 | < 4.5 |
| 70-79 | < 5.5 |
| 80+ | < 6.5 |
Other causes of a rise in PSA level
PSA levels can be higher than normal due to conditions other than prostate cancer.
These conditions include:
- BPH benign prostate hyperplasia (enlargement)
- Prostatitis urinary tract infection
- Recent prostate biopsy
- Recent bladder or prostate surgery
Smaller temporary rises in PSA, for a day or two, can be due to activities that disturb the prostate gland such as a DRE, riding a bicycle or motorbike and recent ejaculation. To reduce the risk of a false positive result, men should abstain from such activities (including sexual intercourse and ejaculation) for 48 hours before having the PSA blood test.
Slow but steadily increasing levels (with symptoms) can mean the presence of prostate cancer. If the PSA level doubles in less than three years the cancer is likely to cause harm within five years.
The “free / total” PSA percentage can be helpful in determining the cause of elevated PSA levels. It may assist in distinguishing between men with prostate cancer and those with other benign conditions.
The “free / total” PSA percentage
PSA is present in the blood in two forms, free (on its own) and bound (attached) to other substances in the blood. Higher levels of free PSA (25% or more) tend to be associated with benign changes in the prostate. Low levels, less than 10%, indicate a strong possibility of prostate cancer.
Table-2 Free-to-Total PSA (for PSA in the range 4-10)
| F/T Ratio | Prostate Cancer Incidence |
| 0-10% | 56% |
| 10-15% | 28% |
| 15-20% | 20% |
| 20-25% | 16% |
| > 25% | 8% |
PSA Velocity
PSA velocity is the measured change in PSA over time. This would require 3-4 PSA tests over a two year period to establish the rate of change. If the PSA velocity is greater than 0.75% per year, for two consecutive years, then it tends to indicate an increased risk of prostate cancer. As a guide, a rising PSA of more than 1.0 per year may require a biopsy, especially in the younger man.
PSA Density
The PSA density is a simple mathematical calculation derived from the division of the PSA by prostate volume. The higher the PSA density, the greater the likelihood of prostate cancer being present. It remains another tool to assess the risk of prostate cancer. A density of greater than 0.15 is more suggestive of a prostate cancer. A density between 0.07 and 0.15 is equivocal, a density of under 0.07 is more suggestive of non-cancerous disease.
The PSA velocity, Free PSA and PSA density assessments are all helpful tools in the assessment of the relative risk for prostate cancer.
What happens if my PSA level is high for my age group?
The assessment of changes in PSA levels prior to diagnosis and treatment is very useful:
- wildly fluctuating levels sometimes associated with prostatic discomfort can mean the presence of inflammation and / or infection (known as prostatitis)
- unchanging levels between 4 and 10 with weakening and slowness of the urinary stream can mean the presence of benign prostate hypertrophy (enlargement)
- slow but steadily increasing levels (with symptoms) can mean the presence of prostate cancer. If the PSA level doubles in under three years the cancer is likely to cause harm within five years
- the “free / total” PSA percentage can be helpful in determining the cause of elevated PSA level. A very low percentage can suggest cancer; a percentage above 25% suggests a benign condition.
Advantages of PSA Testing
- PSA testing increases the chance of detecting prostate cancer at a curable stage.
- Side effects are fewer with an early diagnosis and treatment.
- Most cancers detected with PSA are most likely to cause significant mortality if left untreated.
- A very low PSA level (<2) is very reassuring
Disadvantages of PSA Testing
- PSA testing is not specific to prostate cancer. An elevated PSA level indicates a change in the prostate. This change may be a benign condition. Only 1 in 3 patients with an elevated PSA level will prove to have cancer. This is very similar to the results of mammography for breast cancer.
- Sometimes, a cancer can be present even when the PSA is in the normal range. Unfortunately, this can occur with all diagnostic medical testing.
- Some prostate cancers are not life threatening and therefore may be treated unnecessarily. This is reduced by careful clinical judgment.
How Accurate is a PSA Test?
Although there are still many questions about the value of using PSA to test for prostate cancer it is the best test that is available.
The accuracy of PSA as a tool for detecting prostate cancer is very similar to the accuracy of mammography as a tool for detecting breast cancer. Like mammography the PSA test cannot confirm the presence of cancer. In both cases, when an abnormal test result occurs, further testing is required to obtain a precise diagnosis.
Acknowledgements
Dr. Prem Rashid, Prostate Cancer. The Disease, Treatment Options & Outcomes. 2006
Dr. Phillip D. Stricker, Prof Kerryn Phelps, PSA for the General Practitioner. 2004
Irena Madjar, What women (and their men) need to know about prostate cancer. 2007