BPSA: A Novel Serum Marker for Benign Prostatic Hyperplasia.

Free prostate-specific antigen (fPSA) testing was developed and approved for widespread use despite the lack of knowledge regarding the underlying biologic basis for its ability to discriminate between benign prostatic hyperplasia (BPH) and prostate cancer. We hypothesized that the relationship of total PSA to prostate volume was due primarily to the fPSA component of serum PSA, and we studied the molecular forms of PSA found in prostate tissue. Later, more sophisticated studies resulted in the discovery of BPSA (benign PSA), a novel form of fPSA associated with nodular hyperplasia of the transition zone (TZ). We found that the serum BPSA level is highly correlated with TZ and total prostate volume. In our most recent studies, we found that BPSA correlates better with TZ volume than does PSA and can predict clinically significant prostate enlargement better than PSA or fPSA. Furthermore, the relation of BPSA and fPSA to total prostate and TZ volumes is independent of age.