Columbia-Presbyterian Medical Center discovered a link between the amount of antigen produced per cubic centimeter of tissue (PSA density) and increased cancer risk. By applying these markers to the test, it could be refined even further.
Another Johns Hopkins urologist, Alan Partin, worked with Patrick C. Walsh to develop the Partin Tables—a probability formulary designed to stage prostate cancer and act as a predictor for surgery. The tables continue to be updated and are used by urologists around the world today.
By 1993, Joseph E. Oesterling of the Mayo Clinic promoted the idea that PSA could be age-specific—suggesting that, since younger men have lower antigen levels than older males, doctors should consider different thresholds to trigger follow-ups: At what age does an increase in antigen levels call for a biopsy?
At the time, enough men were undergoing repeated PSA screening that Catalona could show that serial testing improves detection and that by monitoring changes in antigen levels, urologists would have stronger indicators of when to call for