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HelpTest Code PHI11 Prostate Health Index Reflex, Serum
Specimen Required
Patient Preparation:
1. Specimens for testing should be collected prior to prostate manipulations such as digital rectal examination, prostatic massage, transrectal ultrasound, 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.
Supplies: Sarstedt Aliquot Tube 5 mL (T914)
Collection Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions: Within 3 hours of collection, centrifuge, aliquot serum into a plastic vial, and refrigerate. Freeze sample within 24 hours of collection and send frozen.
Useful For
As an aid in distinguishing prostate cancer from benign prostatic conditions in men aged 50 years and older with total PSA between 4.0 and 10.0 ng/mL and digital rectal examination findings that are not suspicious for cancer
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| PHI13 | Prostate Health Index (phi) Reflex | No | No |
Testing Algorithm
This test begins with the analysis of prostate-specific antigen (PSA). If the PSA concentration is between 2.0 and 10.0 ng/mL, then the reflex test will be performed at an additional charge.
If the initial PSA concentration is between 2.0 and 10.0 ng/mL, then free PSA and [-2]pro-PSA isoform results will be reported.
If the initial PSA concentration is between 4.0 and 10.0 ng/mL, then the percent free PSA result and prostate health index (phi) will be calculated and reported.
If the initial PSA concentration is between 2.0 and 4.0 ng/mL, then the percent free PSA result and prostate health index (phi) will not be calculated or reported.
Method Name
Immunoenzymatic Assay
Reporting Name
Prostate Health Index Reflex, SSpecimen Type
Serum RedSpecimen Minimum Volume
0.75 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum Red | Frozen (preferred) | 150 days | |
| Ambient | 24 hours | ||
| Refrigerated | 24 hours |
Reject Due To
| Gross hemolysis | Reject |
| Gross icterus | Reject |
Clinical Information
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 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 total PSA, free PSA, p2PSA, and phi in men undergoing prostate biopsy due to a serum PSA concentration between 4.0 and 10.0 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 total PSA.
Reference Values
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 4.0-10.0 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 4.0-10.0 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% |
Interpretation
The prostate health index (phi) may be used to determine the probability of prostate cancer on biopsy in men aged 50 years and older with total prostate-specific antigen (PSA) in the 4.0 to 10.0 ng/mL range. Low phi scores are associated with a lower probability of finding prostate cancer on biopsy, and higher phi scores are associated with an increased probability of finding prostate cancer on biopsy. The choice of an appropriate phi score to be used in guiding clinical decision-making may vary for each patient and may depend on other clinical factors or family history. The table below indicates the probability of finding prostate cancer on biopsy when total PSA is in the range of 4.0 to 10.0 ng/mL and may be used as guidance for interpreting the phi score.
|
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% |
Cautions
Specimens for [-2]pro-prostate-specific antigen (p2PSA) testing should be collected prior to prostate manipulations such as digital rectal examination (DRE), prostatic massage, transrectal ultrasound, and prostatic biopsy. DRE may cause a transient increase in p2PSA, free prostate-specific antigen (PSA), and PSA.
Transrectal needle biopsy has also been shown to cause transient increases in p2PSA, free PSA, and PSA elevations, thus a 6-week waiting period between needle biopsy and p2PSA, free PSA, and PSA sampling is recommended.
The prostate health index (phi) results should be interpreted in light of the total clinical presentation of the patient, including symptoms, clinical history, data from additional tests, and other appropriate information. The phi should not be interpreted as absolute evidence for the presence or absence of prostate cancer. Elevated PSA concentrations, increased phi, or decreased free PSA may be observed in patients with nonmalignant disorders, as well as those with prostate cancer.
Routine use of 5 alpha-reductase inhibitor drugs typically lower PSA, free PSA, and p2PSA levels in patients. Other drugs used to treat benign prostatic hyperplasia may also affect PSA levels. Care should be taken in interpreting results from patients taking these drugs.
For patient samples containing elevated levels of total protein (>8 g/dL), the possibility exists for interference by total protein. Carefully evaluate the results of patients suspected of having elevated total protein levels.
Free PSA specimens can potentially be falsely decreased by biotin. Biotin should not strongly affect total PSA or p2PSA values.
In rare cases, some individuals can develop antibodies to mouse or other animal antibodies (often referred to as human anti-mouse antibodies (HAMA) or heterophile antibodies), which may cause interference in some immunoassays. Caution should be used in interpretation of results and the laboratory should be alerted if the result does not correlate with the clinical presentation.
The use of the prostate health index (phi) has not been validated when PSA values are outside of the range of 4.0 to 10.0 ng/mL
Method Description
Prostate Specific Antigen:
The Access Hybritech PSA (prostate-specific antigen) assay is a 2-site immunoenzymatic ("sandwich") assay. A sample is added to mouse monoclonal anti-PSA alkaline phosphatase conjugate and paramagnetic particles coated with a second mouse monoclonal anti-PSA antibody. The PSA in the sample binds to the immobilized monoclonal anti-PSA on the solid phase while the monoclonal anti-PSA alkaline phosphatase conjugate reacts with a different antigenic site on the sample PSA. After incubation, materials bound to the solid phase are held in a magnetic field while unbound materials are washed away. The chemiluminescent substrate Lumi-Phos* 530 is added to the vessel and light generated by the reaction is measured with a luminometer. The light production is directly proportional to the concentration of PSA in the sample and is determined from a stored, multipoint calibration curve.(Package insert: Access Hybritech PSA/Prostate-Specific Antigen Instructions for Use. Beckman Coulter Inc; 08/2023)
Free Prostate Specific Antigen:
The Access Hybritech free PSA assay is a 2-site immunoenzymatic ("sandwich") assay. A sample is added to mouse monoclonal anti-free PSA-alkaline phosphatase conjugate and paramagnetic particles coated with a second mouse monoclonal anti-PSA antibody. The free PSA in the sample binds to the immobilized monoclonal anti-PSA on the solid phase while the monoclonal anti-free PSA-alkaline phosphatase conjugate reacts with different antigenic sites on the free PSA molecule. After incubation, materials bound to the solid phase are held in a magnetic field while unbound materials are washed away. The chemiluminescent substrate Lumi-Phos 530 is added to the vessel and light generated by the reaction is measured with a luminometer. The light production is directly proportional to the concentration of free PSA in the sample and is determined from a stored, multipoint calibration curve.(Package insert: Access Hybritech free PSA/Free Prostate-Specific Antigen Instructions for Use. Beckman Coulter Inc; 06/2020)
[-2]ProPSA:
The Access Hybritech p2PSA ([-2]proPSA) is a 2-site immunoenzymatic ("sandwich") assay. A sample is added to mouse monoclonal anti-PSA-alkaline phosphatase conjugate, paramagnetic particles coated with a mouse monoclonal anti-[-2]proPSA antibody, and a blocking reagent. The [-2]proPSA in the sample binds to the immobilized monoclonal anti-[-2]proPSA on the solid phase while the monoclonal anti-PSA-alkaline phosphatase conjugate reacts with different antigenic sites on the [-2]proPSA molecule. After incubation, materials bound to the solid phase are held in a magnetic field while unbound materials are washed away. The chemiluminescent substrate Lumi-Phos*530 is added to the vessel and light generated by the reaction is measured with a luminometer. The light production is directly proportional to the concentration of [-2]proPSA in the sample and is determined from a stored, multipoint calibration curve.(Package insert: Access Hybritech p2PSA/[-2]proPSA Instructions for Use. Beckman Coulter Inc; 10/2023)
Percent free PSA:
The free PSA concentration is divided by the total PSA to derive the percent free PSA. The percentage is provided only when the total PSA is in the range of 4.0 to 10.0 ng/mL.
Prostate health index:
Prostate health index (phi) is calculated in the laboratory information system and provided only when the total PSA is in the range of 4.0 to 10.0 ng/mL.
Day(s) Performed
Monday through Saturday
Report Available
1 to 3 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
84153 - Total PSA
84154 - Free PSA (if appropriate)
86316 - [-2]ProPSA (if appropriate)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| PHI11 | Prostate Health Index Reflex, S | 53764-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| PHI12 | Prostate Specific Antigen, S | 83112-3 |