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Prostate-Specific Antigen (PSA) with Free PSA Fraction and Ratio Calculation

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

This test measures prostate-specific antigen (PSA), a protein produced by the prostate gland, along with its free fraction and ratio to help assess prostate health.

Quick summary

["PSA tests help evaluate prostate health, detect potential issues, and guide treatment decisions."]

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

Key facts at a glance

LOINC
42752-6
Short code
PS IgA B2GP1 indep MoM Ser
Synonyms
PS IgA B2GP1 indep MoM Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
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 PSA Tests Measure

Your blood sample is analyzed for total PSA levels, which reflect overall prostate activity. Additionally, the test measures free PSA, the portion of PSA that isn’t bound to other proteins. The ratio of free PSA to total PSA is calculated to provide more nuanced insights.

Why This Test Matters

Total PSA and free PSA levels can help doctors determine if there’s an abnormal growth in the prostate, such as benign prostatic hyperplasia (BPH) or prostate cancer. The free PSA ratio is particularly useful because it can reduce false positives often seen in PSA tests alone.

When This Test Is Ordered

This test may be recommended during routine check-ups, especially for men at higher risk of prostate issues, or after symptoms like urinary changes, pain, or concerns about prostate health. It can also be used to monitor treatment progress or guide follow-up care.

What to Expect Before the Test

No special preparation is needed, but you may be asked to avoid ejaculation for 2–3 days before the test if it’s part of a broader evaluation. Drink plenty of water the day of the test to help prepare your blood sample.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

PSA Profile

Frequently asked questions

How might PSA test results affect my care?
Elevated total PSA levels can signal potential prostate concerns, but they don’t always mean cancer. Free PSA levels and ratios help doctors assess the likelihood of benign versus malignant causes. Your doctor will interpret results in the context of your symptoms, medical history, and other tests.
What if my PSA levels are high?
If your PSA levels are elevated, your doctor may recommend further testing, such as imaging or a biopsy, to investigate the cause. Lifestyle factors like diet, exercise, and medications can also influence PSA levels, so discussing these with your healthcare provider is important.
Can diet or medications affect PSA test results?
Yes, certain foods (e.g., cruciferous vegetables), supplements (e.g., saw palmetto), or medications (e.g., finasteride, dutasteride) can temporarily alter PSA levels. Your doctor may ask you to avoid these for a period before testing to get more accurate results.
  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