For free PSA, it's all in the numbers.
Check
W A
WA
D006801:Humans; D007118:Immunoassay; D008297:Male; D017430:Prostate-Specific Antigen / Q000097:blood*; D011470:Prostatic Hyperplasia / Q000175:diagnosis; D011471:Prostatic Neoplasms / Q000175:diagnosis*