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Test Code PSAB Prostate Specific Antigen, Total & Free

Important Note

This test may be affected by biotin interference. Patients on high dose biotin (5mg/day or more) should not have samples drawn until at least 24 hours after the last biotin administration.

Specimen and Container/Tube

Specimen Type: Plasma

Preferred Specimen: Mint Top (Li-Heparin)

Other Acceptable specimens: Serum (Red Top or Gold Top SST)

Specimen Handling and Transport Instructions

UCMC Onsite Instructions: 

Collect specimen per standard collection procedure and send to laboratory immediately. 

 

UCMC Offsite and UC MedLab Outreach Instructions: 

  • Samples should be centrifuged within 2 hours of collection.
  • Centrifuge specimens at >2500 x g for 10 minutes at room temperature.
  • Aliquot sample into plastic transport tube containing a minimum of 0.2 mL of specimen.
  • Samples must be sent room temperature at 15-25oC.

Rejection Criteria

  • Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits. 
  • Specimens that are clotted or grossly hemolyzed.
  • Specimens that were transported unspun/whole blood and draw time is greater than 6 hours.

 

Reference Values

 

Test

Age

Sex

Reference Range

Total PSA

All

All

0 - 4.0 ng/mL

Free PSA

All

All

N/A

Free/Total PSA Ratio

All

All

>0.25 ng/mL

Critical Values

None

CPT Codes

84154, 84153

Clinical Indications

The Elecsys free indicated for measurement of fPSA in conjunction with the Elecsys total PSA assay to develop a ratio off PSA to tPSA. This ratio is useful when used in conjunction with the Elecsys total PSA test as an aid in distinguishing prostate cancer from benign prostatic conditions in men age 50 years or older who have a digital rectal examination (DRE) that is not suspicious for prostate cancer and an Elecsys total PSA value in the range 4.00 ng/mL to 10.0 ng/mL. Prostate biopsy is required for the diagnosis of prostate cancer.

Volume

Preferred Volume: 4.0 mL

Minimum Volume: 0.5 mL

 

Specimen Stability

Storage Temperature

Stability

Room temperature

N/A

Refrigerated

5 Days

Frozen

3 Months

 

Collection Instructions

Collect specimen per standard laboratory collection procedures.

Test Components

Total PSA, Free PSA, Free/Total PSA Ratio

Additional Information

  • Approximately 25% of asymtomatic males (age 50 years or older) with PSA levels of 4.1-10.0 ng/mL have prostate cancer, compared to approximately 12% of those with PSA levels of 2.0-4.0 ng/mL.
  • Free/totalP PSA ratios may help to further classify into subgroups with higher or lower cancer rates.
  • Serum tumor markers are not specific for malignancy and should always be interpreted in conjunction with other diagnostic and clinical findings. Results may vary with test methodology.
  • There is no high-dose hook effect at Total PSA concentrations up to 17,000 ng/mL.

 

Limitations:

  • Free & Total PSA values determined on patient samples by differing testing procedures (methods/manufacturers) cannot be directly compared with one another and could be the cause of erroneous medical interpretations.
  • The Elecsys free PSA immunoassay should be used only with the Elecsys total PSA immunoassay to calculate the ratio (%fPSA) of free PSA (fPSA) to total PSA (tPSA).
  • Flutamide at therapeutic daily dosage levels resulted in slightly depressed fPSA values.

Turnaround Time

Turnaround times are relative to the time the specimen is received in the test laboratory. 

 

STAT Turnaround Time: 1 hour

Routine Turnaround Time: 4 hours

Testing Schedule: 24/7

Methodology

Electrochemiluminescence Immunoassay (ECLIA) on the Cobas e immunoassay analyzer

Synonyms/Key Search Words

Free PSA, Total PSA, PSAB, FPSA, PSA Ratio

 

LOINC® Code

12841-3

Last Review Date

6/10/2024