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Prostate-Specific Antigen (PSA) by Immunoassay (Prostate-Specific Antigen Probe)

Published: August 9, 2026Updated: August 16, 2026

This test measures a protein found in higher amounts in men’s prostate gland fluid, often used to screen for prostate cancer or monitor treatment.

Quick summary

["PSA helps assess prostate health but isn’t definitive for cancer alone."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
74539-8
Short code
N men sg A DNA Spec Ql NAA+probe
Synonyms
N men sg A DNA Spec Ql NAA+probe
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-amp-tar
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

PSA (Prostate-Specific Antigen) is a protein produced mainly by the prostate gland. Elevated levels may suggest prostate issues, including inflammation, benign prostatic hyperplasia (BPH), or cancer. This test uses a probe to detect PSA in a blood sample.

Why It’s Done

Doctors may order PSA testing to monitor symptoms of prostate problems, screen for early prostate cancer, or evaluate treatment progress. It’s not a standalone test for cancer diagnosis but can guide further testing.

How It Works

A blood sample is taken and analyzed using an immunoassay method to detect PSA levels. The probe identifies PSA molecules, and results are compared to reference ranges for interpretation.

What to Expect Before the Test

No special preparation is needed, but avoid ejaculation for 2–3 days before testing if possible, as it may slightly lower PSA levels. Drink plenty of water to help with blood draw comfort.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

PSA levels alone don’t diagnose prostate cancer but can signal potential risks. Elevated PSA may prompt additional imaging (like an MRI or ultrasound) or biopsies. Low PSA doesn’t rule out cancer entirely, so results should be discussed with your doctor.

Short name

PSA Probe

Frequently asked questions

What causes PSA levels to change?
Several factors can affect PSA, including age, prostate inflammation (prostatitis), infections, or medications. Lifestyle (e.g., diet, exercise) and recent activities like ejaculation may also influence results.
How often should I get this test?
Your doctor will determine frequency based on your health history, symptoms, and risk factors. Routine screening for men over 50 is debated; discuss personalized timing with your provider.
Can diet or supplements affect PSA levels?
Some studies suggest certain foods (e.g., cruciferous vegetables) or supplements (like zinc or saw palmetto) may influence PSA, but evidence is mixed. Always check with your doctor before making changes.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy