Collection Instructions
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Specimen Type: Serum Red
Patient Preparation:
1. Specimens for testing should be collected prior to prostate manipulations such as digital rectal examination (DRE), prostatic massage, transrectal ultrasound (TRUS), and prostatic biopsy.
2. A 6-week waiting period between needle biopsy and specimen collection is recommended.
3. Specimens should not be collected from patients receiving therapy with high biotin (vitamin B7) doses (ie, >5 mg/day) until at least 8 hours following the last biotin administration.
Collection Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions: Centrifuge, aliquot serum into plastic vial, and refrigerate serum within 3 hours of collection.
Specimen Minimum Volume: 0.75 mL
Specimen Stability Information:
Specimen TypeTemperatureTimeSpecial ContainerSerum RedFrozen150 days
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Result Interpretation
Females: Not applicable
PROSTATE-SPECIFIC ANTIGEN (PSA) Males:
| Age |
Reference range |
| <40 years |
<=2.0 ng/mL |
| 40-49 years |
<=2.5 ng/mL |
| 50-59 years |
<=3.5 ng/mL |
| 60-69 years |
<=4.5 ng/mL |
| 70-79 years |
<=6.5 ng/mL |
| ?80 years |
<=7.2 ng/mL |
PERCENT FREE PSA
Males:
When PSA is in the range of 4-10 ng/mL
| % Free PSA |
Probability of cancer |
| <=10% |
56% |
| 11-15% |
28% |
| 16-20% |
20% |
| 21-25% |
16% |
| >25% |
8% |
PROSTATE HEALTH INDEX (phi)
Males:
When PSA is in the range of 4-10 ng/mL
| phi range |
Probability of cancer |
95% Confidence interval |
| 0-26.9 |
9.8% |
5.2-15.4% |
| 27.0-35.9 |
16.8% |
11.3-22.2% |
| 36.0-54.9 |
33.3% |
26.8-39.9% |
| >=55.0 |
50.1% |
39.8-61.0% |
Calculation of prostate health index (phi) as a part of a reflex test when PSA concentrations are between 4 and 10 ng/mL
Prostate-specific antigen (PSA) is a glycoprotein produced by the prostate gland, the lining of the urethra, and the bulbourethral gland. Normally, very little PSA is secreted in the blood. In conditions of increased glandular size and tissue damage, PSA is released into circulation. Measurement of serum PSA is useful for determining the extent of prostate cancer and assessing the response to prostate cancer treatment. PSA is also used as a screening tool for prostate cancer detection, although its use in screening has become controversial in recent years. While an elevated serum PSA is associated with prostate cancer, a number of benign conditions, such as benign prostatic hyperplasia (BPH) and prostatitis might lead to elevated serum PSA concentrations. As a consequence PSA lacks specificity for prostate cancer detection.
Several PSA isoforms have been identified that can further increase the specificity of PSA for prostate cancer. In particular, the [-2] form of proPSA (p2PSA) shows improved performance over either total or free PSA for prostate cancer detection on biopsy. The prostate health index (phi) is a formula that combines all 3 PSA forms (total PSA, free PSA, and p2PSA) into a single score. phi is calculated using the following formula: (p2PSA/free PSA) x square root of PSA.
In a multicenter study that compared the performance of PSA, free PSA, p2PSA, and phi in men undergoing prostate biopsy due to a serum PSA concentration between 4 and 10 ng/mL, phi was the best predictor of any prostate cancer, high-grade cancer, and clinically significant cancer. At 95% clinical sensitivity, the clinical specificity of phi was 16.0%, compared to 8.4% for free PSA and 6.5% for PSA.
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