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Day to day variation in the measurement of PSA

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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.

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.