To understand the relationship between Prostatitis and PSA you need to understand where PSA comes from, the why..
It is thought that rising blood levels of PSA is brought about by it being liberated into the system because of a disruption of the prostate cellular structure. This can be caused by various prostate diseases, not just prostate cancer. So it is very important to understand that PSA does not only reflect a possibility of prostate cancer but rather, PSA elevations may indicate the possibility of any kind of prostate disease. The most common reason for higher PSA levels includes BHP; benign prostatic hyperplasia, an enlargement of the prostate, and prostatitis (inflammation of the prostate). Indeed, higher PSA levels can also occur with ejaculation, prostate biopsy, prostate examination, urinary retention or catheter introduction. Therefore, when PSA testing takes place, a male should be understand what can influence the results. Also included are age and prostate volume.
So what should be the normal results for a PSA test?
Normal PSA concentrations vary between 1.0 and 4.0 ng/mL. Since the prostate becomes larger producing more PSA as age increases, lower levels in younger men and higher levels in older men are normal. PSA levels can be influenced by ethnicity and genetics (prostate cancer). Changes in PSA results on a yearly basis (PSA-velocity) play a part in decisions about PSA levels. An increase of more than 0.75 ng/mL is used to help decide whether levels may point to disease. Therefore, a man under 55 years of age showing a rise in PSA levels from 0.5 ng/mL to 2.5 ng/mL may warrant concern in terms of velocity, as against a more constant value.
The above information gives you a basic idea of how the PSA test works, and the influence that Prostatitis can have on it at lower levels, especially in the context of single test results, as against PSA velocity results which may indicate a more significant cause.