PSA stands for Prostate Specific Antigen and is a blood test that is used to screen for the presence of prostate cancer. More accurately, the PSA is found in the blood's serum, which is the fluid that the red blood cells and white blood cells travel.
Antigen is a medical or biological term for a substance that stimulates the body to make antibodies.
Prostate is the gland sitting between the urinary bladder and the urethra (the urinary channel that runs through the penis). The prostate's function is to make seminal fluid or semen that is ejaculated during intercourse. Note that sperm is made in the testicles, which is only a small fraction of the seminal fluid.
Prostate Specific Antigen is, therefore, a protein found in the serum that is unique or specific for the prostate. No other tissue, in or out of the body can make Prostate Specific Antigen. The PSA levels can be measured in an individual's serum and with this information we are able to screen for prostate cancer.
PSA is only present in men. PSA is present in all normal prostate tissue. The normal prostate cell holds onto most of the PSA and lets very little leak into the blood stream. The small amount that leaks out is the PSA that is measured by the blood test. Prostate cancer cells actually have less PSA in each cell, but the cancer cell tends to leak more PSA into the blood stream, hence the reason for measuring the PSA levels. Knowing this fact, we have come up with a range of expected values in patients with normal prostate glands. We believe that the PSA value should be less than 4.0. This number is somewhat arbitrary but reflects our feelings that most men (95% or so) with normal prostate glands have a PSA value of 4.0 or less. The catch is the word 'normal'. Any condition that affects the prostate can make the PSA rise. Any type of inflammation of the prostate (prostatitis) can cause the PSA to rise. Most men with prostatitis have no symptoms, but the PSA leaks out the cells and causes the blood PSA level to be higher than normal. Even a simple rectal exam can cause the PSA to rise somewhat. What this means is that PSA is NOT a cancer measurement, and that an elevated PSA does NOT mean you have cancer. The only test that will determine the presence of cancer is a biopsy of the prostate.
First Time Measurement of PSA
(Note: This assumes that the rectal examination found no suspicious nodules or hardness within the gland. Even if ones' PSA level is unmeasurable, a suspicious nodule must be evaluated.)
PSA of 4 or less - If your PSA level has been measured for the first time and is less than 4, we recommend repeating the test on a yearly basis.
PSA between 4 and 10 - If your PSA is greater than 4 but less than 10, we recommend a diagnostic ultrasound of your prostate. If the ultrasound shows no suspicious areas, then nothing further is done. A repeat PSA should be drawn in 4-6 months or no later than one year. If the ultrasound shows a suspicious area, then biopsy of the area needs to be done (usually at the time of ultrasound, if you have been prepared with antibiotics).
PSA greater than 10 - If your PSA is greater than 10, we recommend a diagnostic ultrasound of your prostate with biopsies of the prostate simultaneously. If the ultrasound shows no suspicious areas, then random biopsies of the prostate are taken. If the ultrasound shows suspicious areas, then biopsy of the areas, along with random biopsies needs to be done.
If You've Had Previous Measurements of PSA
(Note: This assumes that the rectal examination found no suspicious nodules or hardness within the gland. Even if ones PSA level is unmeasurable, a suspicious nodule must be evaluated.)
When we have the luxury of previous PSA values, we look at numbers a little bit differently. The PSA level will almost always rise in the face of a cancer that is growing. Any PSA level that is rising is suspicious. As mentioned earlier, the high PSA level may NOT mean that cancer is present. In those cases, we hope to see stable PSA levels. For example, a stable PSA of 15 over a three year period (15,15,15) is probably at less risk than a PSA of 2,3,4 over the same time frame. The second patient's rising levels suggest growth and has to be considered suspicious for cancer. If the first patient with repeating 15 values had a negative biopsy when first discovered, then there is no need to repeat the biopsies. If his levels jumped to 20 or 25 for no apparent reason, then repeat ultrasound and biopsies would be indicated. Recent studies suggest that a 20% rise in PSA in one year should prompt a closer look and possibly an ultrasound and biopsy.