KLK3 and prostate cancer: PSA estimation and various thresholds may be beneficial in the decision to perform a biopsy; in a recent study reporting on thresholds of pre-biopsy PSA for the prediction of advanced prostate cancer (defined as a Gleason score ≥ 7 at biopsy), a PSA ≤ 4.1 carried a negative predictive value of 95.1% [95% confidence interval (CI): 83.0–98.7] for men less than 65 years of age [28].