KLK3 and prostate cancer: Prior to the prostate-specific antigen (PSA, a screening test for detection of prostate cancer) era, studies of the possible association between socioeconomic status (SES) and prostate cancer were inconsistent; however, since the introduction of PSA screening in the late 1980s, a positive correlation is now being reported more consistently, particularly in the U.S.A. [68-71].