Day to day variation in the measurement of PSA
Richard Whittington, MD
Last Modified: September 15, 2002
Dear OncoLink "Ask The Experts,"
I had a radical prostatectomy in 1999 when I was 39 years old. I never had any symptoms. A digital rectal exam prompted the PSA. Prior to surgery, my PSA was 33, 100% of biopsy samples were positive with capsular penetration, Gleason 6-7.
Other than surgery, my treatment included Zoladex beginning 3 days prior to surgery, continuing for ~9 months post surgery, and radiation therapy concurrent with the Zoladex.
- From December 1999 to January 2002, my PSA was 0.00
- In April 2002 my PSA was 0.07
- In August 2002 my PSA was 0.12
Is this just random error in the new lab?
Richard Whittington, MD, Associate Professor of Radiation Oncology at the University of Pennsylvania School of Medicine, responds:
Actually, this is an important question. What you should know is that the day-to-day variation in the measurement of PSA is 0.2. That is why we consider anything less than 0.2 to be undetectable. Also, a small amount of PSA is made by the periurethral glands and we will occasionally see a level of 0.2 and rarely 0.3 that becomes undetectable without any therapy. That is why we consider 0.4 the lowest level needing treatment.