March 16, 2009 -- Question: Why do I need both a digital rectal exam and a PSA test?
Answer: Unfortunately, a digital rectal exam, they only palpate around 10 percent of the prostate gland itself. So by itself it is not very accurate to diagnose prostate cancer. Unfortunately PSA does not detect all prostate tumors. Additional tumors can be detected by a digital rectal exam, so most studies shows that most benefit of detection and screening of prostate cancer, if you use a combination of the prostate specific antigen plus a digital rectal exam.