- What is the PSA test?
- When is the PSA test performed?
- What preparation is needed for the PSA test?
- How is the PSA test performed?
- How are PSA results interpreted?
What is the PSA test?
It is a diagnostic laboratory test identifying the levels of PSA (Prostate-Specific Antigen) in the blood serum of men. PSA is a protein produced both by healthy and cancerous cells of the prostate. PSA is mainly located in the sperm helping semen keep its liquid form, but also appears in small amounts in the blood. High PSA levels in the blood may indicate the presence of prostate cancer. However, other medical conditions as well may increase the PSA value, such as benign prostatic hyperplasia and prostatic inflammation. The highest PSA level circulating in the blood is bound to some proteins (bound or complexed PSA), while a small amount circulates free (free PSA). The sum of bound and free PSA forms the total PSA. The ratio of free/total PSA is used in clinical practice to provide further information about the early diagnosis of prostate cancer.
When is the PSA test performed?
Prostate cancer is the most common type of male cancer. Early diagnosis is important for effective treatment. PSA levels are high in the blood of patients with prostate cancer. The test is conducted as part of the routine check-up of asymptomatic men to detect cancer in early stages. PSA values have to be combined with the Digital Rectal Examination (DRE) of the prostate.
The PSA test is also useful for patients diagnosed with prostate cancer; more specifically, it is used:
- to help the physician decide which is the best time to start a therapy
- to evaluate the effectiveness of a therapy
- to diagnose early any potentia cancer relapse in patients who have already been on therapy.
What preparation is needed for the PSA test?
No special preparation is needed for the PSA test; neither is it required to have an empty stomach for giving blood sample to measure PSA levels. However, you should be aware that there are some conditions that may affect PSA values. For example:
- Ejaculation affects the free PSA concentration; therefore, you should refrain from ejaculating 3 days before the examination.
- Acute prostatitis (prostatic infection) significantly increases PSA values; therefore, the PSA test should be done one month after the completion of its therapy.
Cystoscopy and urethral dilations increase PSA values; therefore, the test should be performed one week later.
How is the PSA test performed?
The test procedure is simple blood sampling. The blood specimen is then taken to the biochemical laboratory. PSA is measured in the blood specimen with the use of special analyzers.
How are PSA results interpreted?
PSA is measured in nanograms per milliliter of blood (ng/mL). There are no absolute cut-off points (thresholds) between normal and abnormal values. Besides PSA values, your physician will also take other factors into account, such as DRE (digital rectal examination), your age and prostate size.
Your physician may probably recommend some biopsy according to the following parameters:
- PSA velocity: change in PSA levels over time. A rapid increase may indicate cancer.
- PSA ratio: the ratio of free to total PSA (free/total PSA). High PSA levels containing a small amount of free PSA increase the likelihood for cancer.