faced a yeoman's task: Proving its validity and creating assays to ensure its accuracy.
In 1987, Stanford University's Thomas Stamey demonstrated that the PSA test—though more sensitive than the prostatic acid phosphotase test—was not very specific, given that levels of PSA may be elevated due to reasons other than cancer (such as age, benign prostatic hyperplasia or prostatitis). True, the test detects early tumors, but at the time, it was also fraught with so many false alarms that many urologists began working to refine the test.
For instance, Scandinavian researchers Hans Lilja and Ulf-Hakan Stenman suggested in 1991 that "free PSA"—unattached antigen floating in the bloodstream—is lower in men with cancer. In 1998, Catalona confirmed that reading both free PSA and total PSA was a better way to determine whether biopsy was needed in a patient with elevated antigen levels.
In 1992, H. Ballentine Carter of Johns Hopkins demonstrated that the rate of rise in PSA levels was greater in men with malignancies, while Mitchell Benson of