How Does a PSA Test Diagnose Prostate Cancer?

A prostate-specific antigen (PSA) test measures a type of protein produced by the prostate gland in men, the increased levels of which may indicate the presence of prostate cancer. While valuable, the PSA does not diagnose cancer but provides doctors the means to spot a developing malignancy in its earliest stages when it is most treatable.

For men who are experiencing symptoms related to prostate cancer, such as difficulty urinating, the PSA test can be an effective screening tool. However, it is notorious for producing false positives and negatives and, as such, is not considered an effective stand-alone test. It is instead used in conjunction with a digital rectal exam (DRE) and ultimately, a prostate biopsy, to either confirm or rule out cancer.

Drawing blood
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How the PSA Test Is Performed

The test consists of a simple blood draw with results generally returned within hours to a few days, depending on the lab.

Typically speaking, a low PSA reading is preferred. Levels above what would be considered normal increases the likelihood of developing cancer. PSAs are measured by nanograms per millimeter (ng/mL) of blood. Most healthy men will have a PSA reading of under 4 ng/mL.

Cause of an Elevated PSA

There are many things that can cause an elevated PSA level. The use of certain medications may result in fluctuations, making it all the more important to tell your doctor about any medications you may be taking, whether they be prescription drugs, over-the-counter medication, or any herbal or homeopathic supplement.

Other factors that affect your PSA level include:

  • Ejaculation within 48 hours of the test
  • An enlarged prostate gland
  • Inflammation of the prostate gland (prostatitis)
  • Older age (PSAs typically increase with age)

For men who have no symptoms of prostate cancer and no other suspicious finding after a DRE, it is typically recommended that the PSA be repeated. If reading is still high, the doctor will most often monitor your PSA on a routine basis or refer you to a specialist urologist for further investigation.

PSA tests are also performed during prostate cancer treatment to check whether levels are falling, ideally to a very low or undetectable level by the end of therapy. Your doctor will then continue to monitor reading to ensure there is no recurrence of cancer.

Urination Problems as a Sign of Prostate Trouble

Men with prostate problems will often have trouble urinating due to the anatomy of the prostate itself. The prostate is a small, walnut-shaped gland that serves many functions in the male reproductive system. The urethra (the tube that allows urine to flow from the bladder to the penis) is surrounded by this gland. As the prostate enlarges, whether due to cancer or other causes, it can constrict the urethra and obstruct the normal urinary flow

Regular medical checkups can help ensure you are being properly screened for cancer and other, more benign abnormalities of the prostate gland.

The bottom line is this: prostate cancer is today the second leading cause of cancer deaths in men in the United States. Do yourself a favor; never skip a checkup.

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Article Sources
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  3. Tarhan F, Demir K, Orcun A, Madenci OC. Effect of ejaculation on Serum Prostate-Specific Antigen concentration. Int Braz J Urol. 2016;42(3):472-8. doi:10.1590/S1677-5538.IBJU.2015.0116

  4. National Institute of Diabetes and Digestive and Kidney Diseases. Prostate problems. Updated March 1, 2016.

  5. American Cancer Society. Key statistics for prostate cancer: prostate cancer facts. Updated August 1, 2019.

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