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.
Lab variability is just one of many things that can change your PSA reading. Urinary tract infections, prostate inflammation, and prostate biopsies often produce sharp spikes in PSA results. According to some studies, ejaculation or a doctor's digital rectal exam can produce smaller rises, at least briefly. And benign prostatic hyperplasia pushes up PSA results as men age. On the other hand, treatment with finasteride (Proscar) or dutasteride (Avodart) will lower the PSA by about 50%. Statins and nonsteroidal anti-inflammatory drugs may also lower the PSA.