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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: PSA Total, Screen with reflex to Free PSA

Test Code(s): PSASRF / HCPSASRF

CPT Code(s): G0103; if reflexed to Free PSA add cpt 84154

Test Description: Test Component:

For patients 50 years of age and older:

Total PSA, and Free PSA if Total PSA is between 4.00 ng/mL and 10.00 ng/mL.

 

For patients <50 years of age:

Total PSA, and Free PSA if Total PSA is between 2.50 ng/mL and 10.00 ng/mL.


Methodology: Chemiluminescent Immunoassay

Days Performed: Daily, 24 hours.

Turnaround Time: Stat: 1 hour.
Routine: 4 hours.


Specimen Requirements

Specimen: Blood

Collection Container: Preferred: Red cap with yellow ring (SST)
Also Acceptable: Red top

Collection Volume: Preferred: 2 mL
Pediatrics: 1 mL

Sample Analyzed: Serum

Volume Required: Preferred: 0.3 mL
Pediatrics: 0.15 mL

Specimen Processing: Centrifuge within 2 hours of collection.  If a complete barrier has not formed, transfer cell-free serum to plastic vial.  Refrigerate.

Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from outreach location. Send frozen if sample will be more than 48 hours old when it arrives.

Stability: Refrigerated: 48 hours
Frozen: 4 months


Interpretation

Reference Interval:

PSA Total Reference Interval:

18 years and up:  0.00-4.00 ng/mL

 

PSA, % Free Interpretive Guidelines:

 

Both total and free PSA determinations were performed at UW Hospital & Clinics using the Siemens Dimension Vista. The free PSA percentage is an aid in distinguishing prostate cancer from benign prostatic conditions in men ages 50 and older with a total PSA between 4.0 and 10.0 ng/mL.  Numerous studies have shown that the % free PSA is generally lower in prostate cancer than in benign prostatic hypertrophy (BPH).  Siemens suggests that a cutoff of 19% or less free PSA (i.e. perform a biopsy at or below this cutoff) yields a sensitivity of 90.2% and specificity of 17.6% in discriminating prostatic cancer from BPH.

 

For patients <50 years of age:

Total PSA, and Free PSA if Total PSA is between 2.50 ng/mL and 10.00 ng/mL.

Test Limitations:

Samples should be obtained before biopsy, prostatectomy or prostatic massage, since manipulation of the prostate gland may lead to elevated PSA levels persisting for up to 3 weeks.

Studies have shown conflicting results on the existence of an effect of digital rectal examination on PSA level. Therefore, when possible, obtain PSA samples before digital rectal examination.

PSA expression may be altered due to hormonal therapy for prostate cancer. Consequently, a low PSA result following a prostatic cancer treatment which includes hormonal therapy may not adequately reflect the presence of residual or recurrent disease.

Results may be affected if patient has developed Human Anti-Murine Antibodies (HAMA) due to exposure to murine based products

Heterophilic antibodies in human serum can react with the immunoglobulins included in the assay components causing interference with in vitro immunoassays. Samples from patients routinely exposed to animals or animal serum products can demonstrate this type of interference potentially causing an anomalous result.

Additional Information:

The PSA assay may be used in conjunction with a digital rectal exam as a screening test for prostate cancer.

Prostate

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