What is a PSA Blood Test?

A prostate-specific antigen (PSA) blood test detects whether high levels of a protein are present in a man’s body. Elevated PSA, which is a product of the prostate gland, can signal that the patient has prostate cancer. A PSA blood test also is used to detect less serious conditions, such as an enlarged or inflamed prostate. The PSA blood test is controversial among some medical professionals because of concerns over false-negative and false-positive results and questions about whether the screening saves lives.

A PSA test is performed by a drawing blood from a man. The blood is tested by medical technicians in a laboratory. The results are sent to the doctor, who interprets the data. The analysis is usually performed on men who are age 50 or older as part of prostate screening. It often is used in conjunction with other prostate checkups, such as digital rectal exams.

PSA is a naturally occurring protein produced in prostate gland cells, and most men maintain a low level of the antigen. The amount of antigen rises slightly with age. A normal PSA level for middle age and elderly men is considered 4 or less nanograms per milliliter (ng/ml). A PSA blood test that shows elevated levels higher than 4 ng/ml may indicate prostate problems. Younger men have a lower baseline antigen amount of about 2.5 ng/ml or less, and anything higher for younger men could be a sign of prostate ailments.

Prostate cancer is one cause of high antigen levels that the test might detect. The blood test along with a digital rectal exam checks for the presence of cancer. Unusual results will lead to more invasive examinations, such as biopsies of suspicious masses. Used together, these screenings can help physicians discover asymptomatic prostate cancer before it advances.

High PSA levels also may indicate less serious prostate conditions. Elevated antigen amounts in a PSA blood test could signal an inflamed prostate, a condition called prostatitis. Another possible cause is an enlarged prostate, known as benign prostatic hyperplasia.

A PSA blood test cannot distinguish between prostate afflictions. Unusual antigen levels will prompt more tests to determine what, if any, prostate ailment is present. Companion assessments may include digital rectal exams, urinalysis, and blood creatinine work ups. The combined results of all screenings help doctors correctly diagnose a patient.

Controversy surrounds PSA screening. Some men have experienced false-positives, which wrongly indicate a problem and lead to unnecessary further testing. More invasive prostate screening could result in incontinence or erectile dysfunction. Others have had false-negative outcomes, or the failure of tests to detect an existing disease, which can allow a condition to advance untreated. Some physicians suggest that PSA tests have not been proven to be valid and therefore could be an unnecessary medical intervention.