Adjust PSA for prostate volume to improve cancer detection.
PSAD = PSA / Prostate Volume. A PSAD ≥ 0.15 ng/mL/cc suggests a higher probability of prostate cancer, while lower values favor BPH (larger prostates produce more PSA). PSAD is useful when PSA is in the "gray zone" (4–10 ng/mL). Prostate volume is measured by transrectal ultrasound or MRI.