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Test ID: PSAFT Prostate-Specific Antigen (PSA), Total and Free, Serum

Reporting Name

PSA Total and Free, S

Useful For

Assessing the risk of prostate cancer in patients with borderline or moderately increased total PSA (4.0-10.0 ng/mL)

 

Determining which patients should have follow-up prostate biopsy

Clinical Information

Prostate-specific antigen (PSA) is a glycoprotein that is produced by the prostate gland, the lining of the urethra, and the bulbourethral gland. Normally, very little PSA is secreted in the blood. Increases in glandular size and tissue damage caused by benign prostatic hypertrophy, prostatitis, or prostate cancer may increase circulating PSA levels.

 

PSA exists in serum in multiple forms: complexed to alpha-1-anti-chymotrypsin (PSA-ACT complex), unbound (free PSA), and enveloped by alpha-2-macroglobulin (not detected by immunoassays).

 

Higher total PSA levels and lower percentages of free PSA are associated with higher risks of prostate cancer.

 

Most prostate cancers are slow growing, so the utility of prostate cancer screening is marginal in most men with a life expectancy of less than 10 years.

Interpretation

When total prostate-specific antigen (PSA) concentration is below 2.0 ng/mL, the probability of prostate cancer in asymptomatic men is low, further testing and free PSA may provide little additional information. When total PSA concentration is above 10.0 ng/mL, the probability of cancer is high and prostate biopsy is generally recommended.

 

The total PSA range of 4.0 to 10.0 ng/mL has been described as a diagnostic "gray zone," in which the free:total PSA ratio helps to determine the relative risk of prostate cancer (see table below). Therefore, some urologists recommend using the free:total ratio to help select which men should undergo biopsy. However, even a negative result of prostate biopsy does not rule-out prostate cancer. Up to 20% of men with negative biopsy results have subsequently been found to have cancer.

 

Based on free:total PSA ratio: the percent probability of finding prostate cancer on a needle biopsy by age in years:

Free:total PSA ratio

50-59 years

60-69 years

70 years and older

≤0.10

49%

58%

65%

0.11-0.18

27%

34%

41%

0.19-0.25

18%

24%

30%

>0.25

9%

12%

16%

Analytic Time

1 day

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.-10 p.m.

Saturday; 8 a.m.-5 p.m.

Clinical Reference

1. Catalona WJ, Smith DS, Wolfert RL, et al: Evaluation of percentage of free serum prostate-specific antigen to improve specificity of prostate cancer screening. JAMA 1995:274(15);214-1220

2. Oesterling JE, Jacobsen SJ, Klee GG, et al: Free, complexed and total serum prostate specific antigen: the establishment of appropriate reference ranges for their concentrations and ratios. J Urol 1995;154:1090-1095

3. Duffy MJ. Biomarkers for prostate cancer: prostate-specific antigen and beyond. Clin Chem Lab Med. 2020 Feb 25;58(3):326-339

4. Catalona WJ: Prostate Cancer Screening. Med Clin North Am. 2018 Mar;102(2):199-214

Method Name

Electrochemiluminescent Immunoassay (ECLIA)

Specimen Type

Serum


Advisory Information


This test should be ordered only in patients with a total PSA between 4-10 ng/mL.



Necessary Information


Include patient's age.



Specimen Required


Patient Preparation: For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.

Supplies: Aliquot Tube, 5 mL (T465)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot serum within 3 hours of collection.


Specimen Minimum Volume

0.75 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Frozen 90 days

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

84153

84154

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PSAFT PSA Total and Free, S 53764-7

 

Result ID Test Result Name Result LOINC Value
TPSA Total PSA 83112-3
FPSA Free PSA 83113-1
PSA_R Free PSA/PSA Ratio 12841-3

Forms

If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-General Request (T239)

-Oncology Test Request (T729)

Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-Neuroimmunology, mml-Neuro-oncology, mml-Pediatric