Test Guide Mobile

Free PSA
Also known as : [Prostate Specific Antigen (Free and Total)]

Blood
Test performed by: LabPLUS Automation

This test may be vetted by a pathologist.

The clinical information for the test must be clearly written on the request form. If clinical information is not provided, or does not provide sufficient justification for the test, the test may be declined.

Declined tests :

If a test is declined, the specimen will be held for a reasonable period (usually 3 weeks but dependant on the stability of the sample). Medical practitioners seeking approval for a declined test should email the on-call Chemical Pathologist ( chemicalpathologist@adhb.govt.nz ) , giving the patient's name and NHI number and the clinical justification for the test. If unable to email, call the on-call Chemical Pathologist via Lablink (09-3078995) and identify yourself as a doctor.

Test vetting policy

IMPORTANT EXTERNAL REFERRERS:

Sample to be centrifuged, separated and frozen within 3 hours of Collection.

Sample stability:

8 hours at 20-25 ^o C
5 days at 2-8 ^o C
12 weeks at -20 ^o C

Specimen Collection
4.5 mL PST Plasma (Preferred)
5 mL Heparin Blood
4 mL Plain Serum
3.5 mL SST Serum
Reference Intervals
Uncertainty of Measurement : 10% below level of 0.5 ug/L

6% above level of 2 ug/L

Assay Method
Principle: Sandwich type immunoassay with chemiluminescence detection
Reagents: Roche free PSA

Analyser: Cobas e801

Diagnostic Use and Interpretation
Free PSA is a specialist test. Its diagnostic sensitivity and specificity are not considered useful enough to confidently rule in or rule out prostate cancer in the primary care setting.
Free PSA is not included the 2015 NZ prostate cancer management and referral guideline, accessed via https://www.health.govt.nz/publication/prostate-cancer-management-and-referral-guidance (last accessed 8 ^th April, 2019).

After consultation with local urologists, Free PSA testing at LabPlus will ONLY be approved when requested by a urologist, or with prior approval of a urologist or chemical pathologist documented on the request form. All other requests will be rejected.

Free PSA will NOT be approved if the total PSA is <2 ug/L or >10 ug/L.

Monitoring using serial percentage free PSA to predict risk of prostate cancer is not recommended. It also has no role in monitoring patients post prostatectomy for CA prostate.

Percentage Free PSA at:

1. >25% - is statistically associated with low risk for prostate cancer (however, risk increases with increasing age)

2. <10% - is statistically associated with at least 50% risk for prostate cancer, regardless of age

3. 10-25% - is statistically associated with intermediate risk for prostate cancer

Where suspicion is high based on clinical judgement, or when total PSA is below age related referral cut points but previous percentage free PSA has been <10%, more definitive testing (e.g. MRI and prostate biopsy) should be considered after consultation with the Urology service.

Contact Information
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.

If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).

Individual chemical pathologists may be contacted but will not be available at all times.

After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.

Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402

Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052

Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427

Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427

Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427

Last updated at 15:26:00 06/01/2025