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- PSA Total:Free Ratio Reflex
Test Includes
Total PSA; free PSA when total is between 4.0 and 10.0 ng/mL. If reflex testing is performed, additional charges/CPT code(s) may apply.
Special Instructions
Specimens should not be drawn immediately after digital rectal examination (DRE), prostatic massage, or transrectal ultrasound (TRUS). PSA sampling should not be performed for at least six weeks after prostatic biopsy.
Values obtained with different assay methods should not be used interchangeably in serial testing. It is recommended that only one assay method be used consistently to monitor each patient's course of therapy. This procedure does not provide serial monitoring. It is intended for one-time use only. If serial monitoring is required, please use the serial monitoring number 480640 to order.
Expected Turnaround Time
Within 1 day
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Related Information
Related Documents
Specimen Requirements
Specimen
Serum (preferred) or plasma
Volume
1 mL
Minimum Volume
0.7 mL (Note: This volume does not allow for repeat testing.)
Container
Red-top tube, gel-barrier tube, or green-top (lithium heparin) tube. Do not use oxalate, EDTA, or citrate plasma.
Collection
If a red-top tube or plasma is used, transfer separated serum or plasma to a plastic transport tube.
Storage Instructions
Maintain specimen at room temperature.1
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 3 days |
Refrigerated | 3 days |
Frozen | 14 days |
Freeze/thaw cycles | Stable x3 |
Causes for Rejection
EDTA plasma specimen
Test Details
Use
Measure the percentage of free (uncomplexed) PSA relative to the total amount of PSA in men with serum PSA concentrations between 4.0 and 10.0 ng/mL.
Limitations
The interpretive guidelines provided for percent free PSA are based on a population of men with normal digital rectal exam (DRE) and total PSA between 4.0 and 10.0 ng/mL. Catalona and coworkers2 did not make specific recommendations regarding the use of percent free PSA for any other population of men.
Patients taking finasteride, an alpha-reductase inhibitor, will have diminished levels of PSA. PSA complexes are more stable than free PSA.1 The serum levels of both total and free PSA increase with prostate manipulation but the free returns to premanipulation concentrations quicker. This can result in a transient elevation in percent free PSA.
Methodology
Electrochemiluminescence immunoassay (ECLIA)
Additional Information
In general, serum PSA levels increase due to physical changes to prostate architecture caused by trauma, infection, inflammation, prostate manipulation, benign prostatic hypertrophy (BPH), or malignancy.3,4 The sensitivity of PSA levels to these changes serves as the basis for the clinical use of the test. The PSA concentration in the serum of healthy men is a millionfold lower than that in seminal fluid. PSA in seminal fluid is predominantly free or uncomplexed. In serum, the majority of PSA is bound to inhibitors, including α1-antichymotrypsin (ACT) and α2-macroglobulin (A2M). Measured total PSA consists of free and ACT-bound, since PSA complexed to A2M is not immunologically detectable.
Catalona and coworkers found that one in four patients with normal DRE and PSA levels between 4.0 and 10.0 ng/mL have prostate cancer.2 They recommend using a cutoff of 25% free PSA for this group of men (see Limitations) to identify individuals with an increased risk of prostate cancer. They found that 95% of men with cancer (as determined by biopsy) with normal DRE and total PSA between 4.0 and 10.0 ng/mL had percent free PSA of ≤25%. Their study further indicated that 20% of men with benign disease (as determined by biopsy) with normal DRE and a total PSA between 4.0 and 10.0 ng/mL had percent free PSA greater than the 25% cutoff.
Alternatively, percent free PSA may be used to determine the relative risk of prostate cancer in individual men.2 The following table lists the probability of prostate cancer for men with nonsuspicious DRE results and total PSA between 4.0 and 10.0 ng/mL, by patient age (see Limitations). See table.
% Free PSA | 50 to 64 Years | 65 to 75 Years |
|---|---|---|
0.00−10.00 | 56% | 55% |
10.01−15.00 | 24% | 35% |
15.01−20.00 | 17% | 23% |
20.01−25.00 | 10% | 20% |
>25 | 5% | 9% |
Footnotes
1. Woodrum D, French C, Shamel LB. Stability of free prostate-specific antigen in serum samples under a variety of sample collection and storage conditions. Urology. 1996 Dec; 48(6A Suppl):33-39.8973697
2. Catalona WJ, Partin AW, Slawin KM, et al. Use of percentage of free prostate-specific antigen to enhance differentiation of prostate cancer from benign prostatic disease. A prospective multicenter clinical trial. JAMA. 1998 May 20; 279(19):1542-1547.9605898
3. Sokoll LJ, Chan DW. Prostate-specific antigen. Its discovery and biochemical characteristics. Urol Clin North Am. 1997 May; 24(2): 253-259.9126221
4. Polascik TJ, Oesterling JE, Partin AW. Prostate-specific antigen: A decade of discovery--what we have learned and where we are going. J Urol. 1999 Aug; 162(2):293-306.10411025
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 480772 | PSA Total (Reflex To Free) | 010334 | Prostate Specific Ag | ng/mL | 2857-1 | |
| 480772 | PSA Total (Reflex To Free) | 480647 | Reflex Criteria | N/A |
| Reflex Table for Prostate Specific Ag | ||||||
|---|---|---|---|---|---|---|
| Order Code | Order Name | Result Code | Result Name | UofM | Result LOINC | |
| Reflex 1 | 480848 | %fPSA Reflex | 480853 | PSA, Free | ng/mL | 10886-0 |
| Reflex Table for Prostate Specific Ag | ||||||
|---|---|---|---|---|---|---|
| Order Code | Order Name | Result Code | Result Name | UofM | Result LOINC | |
| Reflex 1 | 480848 | %fPSA Reflex | 480797 | % Free PSA | % | 12841-3 |
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