Harvard Men's Health Watch

On call: PSA variability

Q. I've been tracking my PSA ever since I turned 50, 11 years ago. Since I just moved from St. Louis to Denver, my next test will be done in a new lab. Will the change in labs affect my levels?

A. It's a good question. PSA testing is performed in hundreds of labs in all parts of the country. Most use approved commercially available PSA assays, but many companies produce these testing kits. When researchers used five different kits to test blood samples from 596 men, they found that results ranged from 13% lower to 15% higher than their standard. If you are following your results very closely, a change in the testing method could produce a blip in your readings.

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