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Microbiology & Infection
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Prostate specific antigen is a protein made by cells of the prostate, a small gland that helps produce semen. The PSA blood test measures how much of this protein is circulating in your bloodstream. Small amounts are normally present, and levels can change for many reasons related to prostate health.
Clinicians use PSA together with your history and physical exam to assess the prostate. It may be used for screening after a shared decision-making discussion, to evaluate urinary or prostate symptoms, and to monitor known prostate conditions or response to treatment.
PSA can rise with prostate cancer, but it can also increase with noncancer conditions such as benign prostate enlargement, inflammation, or recent procedures affecting the prostate. The test does not diagnose cancer by itself; it helps estimate the likelihood that more evaluation could be useful.
Your clinician may order PSA as part of screening if you are at increased risk based on age, family history, or ancestry, or to follow symptoms or treatment. Possible benefits include finding cancers before symptoms appear. Potential downsides include false alarms, extra testing like biopsy, and discovering slow-growing cancers that may never cause harm. Talking with your clinician about your values and preferences can help decide if and when PSA testing is right for you.
A single PSA value is only one piece of the picture. Your clinician will interpret it in the context of your age, prostate size, medications, prior results, and any urinary or prostate symptoms. Trends over time and the specific laboratory method are important, so repeat testing may be recommended for confirmation.
If your result is higher than expected, your clinician may repeat the test, address any infection or inflammation, or ask you to avoid activities that can temporarily raise PSA before retesting. Further evaluation might include a rectal exam, urine tests, imaging, or biopsy if indicated. If your result is low or stable, monitoring at appropriate intervals may be all that is needed. After prostate treatment or surgery, the pattern of PSA over time helps track response and plan follow-up.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Ejaculation or prolonged bicycling in the days before the test can temporarily raise PSA. Avoid these activities for a short period before blood is drawn if your clinician advises.
A prostate biopsy, urinary catheter placement, cystoscopy, or significant manipulation of the prostate can elevate PSA for a while. Testing is often delayed until the prostate has had time to recover.
Prostatitis or a urinary tract infection can raise PSA. Testing is best done after symptoms resolve and any treatment is completed, to avoid confusing results.
Medicines such as finasteride or dutasteride used for prostate enlargement can lower PSA. Tell your clinician about these medications so your result can be interpreted correctly.
Testosterone therapy and some supplements may increase PSA by stimulating prostate tissue. Share all prescription and nonprescription products you use with your clinician.
PSA tends to be higher with older age and larger prostate volume, even without cancer. Your clinician considers these factors when assessing your result.
PSA can vary slightly from test to test and between laboratories. Using the same lab when possible and repeating the test when results are unexpected can improve accuracy.
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