KLK3 and metastatic neoplasm: Prostate-specific antigen greater than 100 ng ml−1 has been found to be the single most important indicator of metastatic disease, with a predictive value of 100% (Rana et al, 1992), whereas the negative predictive value of PSA less than 20 ng ml−1 has been found to be about 99% (Oesterling, 1991).