The prostate-specific antigen (PSA) test measures blood levels of a protein called prostate-specific antigen, which is produced by prostate cells. PSA often rises in men who have prostate cancer. But an elevated PSA level doesn’t always mean that a man has the disease. Conversely, a normal PSA level doesn’t always mean he doesn’t have it. Here’s what men should know about factors that can affect their PSA test results.
PSA screening produces a significant number of false alarms, since PSA levels in the blood may be elevated for reasons other than prostate cancer. These include:
- Prostatitis, an inflammation of the prostate
- Benign prostatic hyperplasia (BPH), an enlargement of the prostate
- Ejaculation within 48 hours before the test
Some evidence implicates digital rectal exams and bicycle riding within 48 hours before the test as causes of increased PSA levels as well.
Based on findings from large screening trials, most doctors would consider a PSA above 3 ng/mL to 4 ng/mL in men between 50 to 70 years of age to be a reason for further evaluation, especially if it is rising.
Two drugs used to treat prostate enlargement, finasteride (Proscar) and dutasteride (Avodart) lower PSA levels by about 50 percent. You should have a PSA test before starting treatment with either drug so that subsequent PSA values can be interpreted in light of this baseline value. If you’re already taking one of the drugs and your baseline PSA level wasn’t obtained, your current PSA test results should be doubled to estimate your true PSA level.
The medication Propecia, which is a lower dose of finasteride marketed for the treatment of male-pattern baldness, also lowers a PSA value to the same extent as the larger dose of finasteride. If you use Propecia, alert your doctor so your PSA results can be adjusted accordingly.