What is PSA? PSA stands for prostate specific antigen, which is a protein produced by both normal and cancerous cells of the prostate gland. It is used as a screening test for prostate cancer; although this is met with controversy. It is also used to assess response to the treatment of prostate cancer.
The PSA value increases with increasing age because the prostate gland size increases. As a result, the normal reference range may be appropriate based upon a man’s age. This may help understand what a true normal or abnormal number may be and help avoid needless biopsies in older men.
It is also known that different races have different PSA values; black men in particular tend to have higher PSA values than white men without cancer. As a result, there is discussion that the PSA value should be race dependent. This is still unclear, but you can see the issues surrounding PSA values.
It is interesting that the higher the BMI (obesity) the lower the PSA values tend to be. This may be due to higher plasma volume. If that is the case, consider the importance of the rectal exam (o joy!).
There are some medications that lower the PSA value (5-apha reductase inhibitors). When on such meds (i.e. finasteride) the PSA interpretation need be adjusted. Some say any increase in PSA value while on these meds need to be evaluated.
Other medications such as the cholesterol lowering statins (ex: Lipitor) also appear to be able to lower PSA values. So maybe a two-fer? Lower cholesterol AND lower PSA? It appears promising, if you like statins.
What are other causes for elevated values? There are several major causes of elevated PSA values: BPH (benign prostatic hypertrophy (enlarged prostate)); prostate cancer; inflammation and trauma.
Of these, BPH is the most common especially for men over 50 years old. Simply put, bigger prostates produce more enzymes. Unfortunately, it is not that simple, as bigger prostates may also have pockets of cancer as well. In addition, treatment of BPH may lower PSA values. What to do? Work closely with your doctor.
Prostatitis is another common cause. As a result many physicians will treat an elevated PSA value with antibiotics for presumed infection than repeat the PSA after four weeks or so. This approach is also controversial as to its effectiveness; it is however the usual practice.
In regard to trauma, vigorous bike riding may elevate the PSA value as can a digital rectal exam. Although not proven, the blood test probably should be checked before the exam or after a time of biking abstinence.
Other methods for screening prostate? There is something called PSA density that you may hear about to more accurately predict cancer if you have an elevated PSA value. This is the volume of prostate as measured by ultrasound. The density would be the PSA divided by the volume. This is also controversial as there are different standards regarding the measurements with the ultrasound.
The approach that has gotten the most traction is something called PSA velocity, or the rate of change of the PSA over time and not so much the actual value. This velocity seems more related to the risk of death from prostate cancer.
So, PSA is a valuable tool for prostate cancer but is not specific for cancer. The use of PSA velocity or density has not proven of great use. Thus, the number of biopsies done is still too high. The value of checking PSA seems higher the younger you are (starting age 40-50).