<prompt> Which of the following is not a variant of PSAPSA densityPSA nodularityPSA velocityRatio of free to bound PSA  <response>: In the past, most doctors considered PSA levels of 4.0 ngmL and lower as normal. Therefore, if a man had a PSA level above 4.0 ngmL, doctors would often recommend a prostate biopsy to determine whetherprostate cancer was present. 