A prostate-specific antigen (PSA) test can detect prostate cancer early, according to the American Cancer Society. When a PSA level is above 4 ng/ml, it prompts doctors to perform additional tests which can diagnose cancer.
PSA is secreted by the prostate gland and in healthy men, it tends to stay under 4 ng/ml. The higher the level is, the higher the risk of prostate cancer being present. However, a blood test to learn the PSA level is not an exact indicator of cancer and further testing needs to be performed. This can include a biopsy as other factors, such as poor health, can cause a high PSA level.