To the Editor: I would like to comment on the study by Jacobsen et al1 published in the January 2012 issue of Mayo Clinic Proceedings that documented the changes in serum prostate-specific antigen (PSA) values in a large group of men. The authors determined that the median annual change in PSA was about 4.8%, while the 95th percentile for PSA increase was about 50%. Interestingly, while the baseline PSA values and the absolute increases in PSA values increased with age, the increases in PSA were relatively constant across all ages when expressed as a percentage of the baseline value. They propose that PSA velocity, expressed as a percentage increase over the baseline PSA, may have more utility as an indication for biopsy than using a fixed annual increase in PSA. For example, men in their 50s had a median baseline PSA of 0.9 ng/mL, so the 95th percentile increase would be about 0.45. For men in their 70s, with a median baseline PSA of 2.1, the 95th percentile increase would be about 1.05. These examples show how using a percent increase in PSA as a biopsy threshold might prove more adaptive to age-related variations than using a fixed absolute annual increase of 0.75 points, as has been proposed in the past. Much work needs to be done in this area to validate these findings. Many physicians will choose to follow the reasonable recommendation of the US Public Health Service not to screen for PSA in any category of healthy men until stronger evidence of benefit emerges.2 But for those who believe that there is a useful signal buried in all the noise of PSA measurements, perhaps this study is the first step in developing a prostate cancer screening algorithm that will prove robustly beneficial for men across a range of ages and baseline PSA values. As a primary care physician who is stubbornly biased in favor of PSA testing, I would be interested to see further research into the utility of adaptive algorithms when testing PSA.