What is assay of serum PSA in prostate cancer?

Normal value is <4, Endourethral maneuvers, prostate biopsies and surgery lead to rise in PSA, while DRE, prostate massage, endorectal US or ejactulation lowers levels of PSA <1. Pt w/prostate hyperplasia taking 5a reductase inhibitors drugs should be taken into account when assessing PSA level