Prostate Health Index (PHI)
A calculated score that combines total PSA, free PSA and p2PSA to estimate how likely a biopsy is to find prostate cancer when total PSA is mildly raised.
AI-verified against cited sources. Awaiting expert reviewAlso called PHI, phiLOINC 97150-7
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What it is
The Prostate Health Index (phi) is a score the lab calculates, not a separate blood test. From one blood sample, the lab measures total PSA, free PSA and a form of PSA called p2PSA (also written [-2]proPSA). It puts the three numbers into a formula, and a higher score goes with a higher chance that a biopsy will find prostate cancer. The score is meant for men 50 and older whose total PSA is between 4.0 and 10.0 ng/mL and whose rectal exam did not look suspicious. Mayo does not report it outside that PSA range.
Why it matters
A mildly raised PSA has many possible causes, and most are not cancer. In this middle range, a biopsy often finds nothing. phi is one of several add-on tools, along with percent free PSA, other blood or urine tests and MRI, that can help you and your clinician decide whether to go further. In Mayo's table, cancer was found in about 10 of 100 men with a score under 27 and in about 50 of 100 men with a score of 55 or higher. The AUA guideline says clinicians may use add-on tests like this when the extra information would change the decision about a biopsy. That is a conditional recommendation based on limited evidence. phi does not diagnose cancer.
If it’s low
A lower phi means a lower chance that a biopsy will find prostate cancer, but it does not rule cancer out. In Mayo's table, cancer was still found in 9.8% of men with a score under 27.
Common causes
- A noncancerous cause of a mildly raised PSA, such as an enlarged prostate
- Prostate cancer is still possible, at a lower chance
What can help
- Ask your clinician when to repeat PSA testing
- Ask whether following your PSA over time makes sense for you
If it’s high
A higher phi means a higher chance that a biopsy will find prostate cancer. It does not mean that you have cancer. In Mayo's table, cancer was found in 33.3% of men with a score of 36.0 to 54.9 and in 50.1% of men with a score of 55.0 or higher. Other prostate conditions can also raise the score.
Common causes
- Noncancerous prostate conditions that raise PSA, such as an enlarged prostate or inflammation (Mayo notes phi can rise in nonmalignant disorders too)
- Prostate cancer
What can help
- Ask your clinician how phi fits with your PSA trend, rectal exam, family history and any MRI
- Ask whether to repeat PSA testing after an infection or procedure has settled
- Tell your clinician about any 5-alpha-reductase inhibitor medicine you take, since these lower PSA, free PSA and p2PSA
What can affect your result
- Total PSA: phi is only validated when total PSA is 4.0 to 10.0 ng/mL
- Age: it is intended for men 50 and older
- A rectal exam, prostate massage, ultrasound probe or biopsy shortly before the draw
- 5-alpha-reductase inhibitor medicines, which lower PSA, free PSA and p2PSA
- High-dose biotin supplements, which can lower free PSA falsely
- The assay maker: the score was developed on Beckman Access assays, and results differ on other makers' assays
- Rare interfering antibodies in the blood, and very high total protein
- Mayo asks that blood be drawn before a rectal exam, prostate massage, transrectal ultrasound or prostate biopsy, because these can cause a short-lived rise in p2PSA, free PSA and PSA. It recommends waiting about 6 weeks after a needle biopsy.
- 5-alpha-reductase inhibitor medicines typically lower PSA, free PSA and p2PSA, so phi is harder to interpret in people who take them. Other medicines for an enlarged prostate may also affect PSA.
- Biotin (vitamin B7) can falsely lower free PSA on these assays. Mayo asks that blood not be drawn within 8 hours of a high biotin dose (over 5 mg a day).
- Rare antibodies in the blood (human anti-mouse or heterophile antibodies) can cause false results on some immunoassays, and total protein over 8 g/dL can interfere.
- phi was developed and validated on the Beckman Access Hybritech assays, and results differ with other makers' assays.
- Mayo accepts serum in a plain red-top tube (not a gel tube) and asks that serum be separated and refrigerated within 3 hours of the draw.
A temporary rise from a rectal exam, biopsy or infection fades over days to weeks. Mayo recommends waiting about 6 weeks after a needle biopsy.
When to talk to a clinician
A phi score has no urgent cutoff. Ask your clinician what your score means for next steps. Talk with your clinician soon if you have blood in your urine or semen, trouble passing urine, or new pain in your hips, back or pelvis. Get urgent care if you cannot pass urine, or if you have fever and chills with painful urination.
Questions you could ask
- Is phi a good test for me, given my total PSA and age?
- Could a medicine, supplement or recent procedure have changed my result?
- How does my phi score fit with my PSA trend, my exam and any MRI?
- What would be the next step for someone with my score?
- Does a lower phi change when we should repeat my PSA?
- Is there anything else we should check, such as an MRI or another test?
Questions people ask
How is the phi score calculated?
The lab multiplies the ratio of p2PSA to free PSA by the square root of total PSA. In plain terms, a higher p2PSA, a lower free PSA and a higher total PSA all push the score up. You do not need to calculate it yourself: the lab reports the finished score.
Why does my report not show a phi score?
Labs usually calculate phi only when total PSA is in a middle range. Mayo, for example, reports it only when total PSA is 4.0 to 10.0 ng/mL, because the score has not been validated outside that range. Some labs run a wider range. Your clinician can tell you whether the test is worth adding.
Does a low phi mean I can skip a biopsy?
A low score means a lower chance of finding cancer, not zero. In Mayo's table, cancer was found in about 10 of 100 men with a score under 27. Mayo cautions that phi should not be read as proof for or against cancer. Whether to do more testing is a decision for you and your clinician, using your PSA history, exam, family history and other tests.
Show the science and sources
For clinicians and researchers
phi = (p2PSA ÷ free PSA) × √(total PSA), where p2PSA is the [-2]proPSA isoform in pg/mL and free and total PSA are in ng/mL (Catalona 2011). The Beckman Access Hybritech p2PSA, free PSA and total PSA assays are used; Mayo's phi test is calculated in the laboratory information system and reported, with percent free PSA, only when total PSA is 4.0 to 10.0 ng/mL, while its reflex version measures free PSA and p2PSA when PSA is 2.0 to 10.0 ng/mL but still reports phi only when PSA is 4.0 to 10.0 ng/mL. Mayo states that phi has not been validated outside 4.0 to 10.0 ng/mL, is for men 50 and older with a non-suspicious rectal exam, and should not be read as absolute evidence for or against cancer. In the pivotal multicenter study (892 men aged 50 and older, PSA 2.0 to 10.0 ng/mL, normal rectal exam), phi had higher specificity than total PSA or percent free PSA at 80% to 95% sensitivity, and an AUC of 0.703 for any cancer, and 0.724 versus 0.670 for percent free PSA for Gleason 4+3 or higher cancer (Catalona 2011). At 95% sensitivity, specificity was 16.0% for phi versus 8.4% for percent free PSA and 6.5% for total PSA (Catalona 2011). The probability groups Mayo prints (0–26.9, 27.0–35.9, 36.0–54.9 and 55.0 and above) differ slightly from the groups in that paper (0–24.9, 25.0–34.9, 35.0–54.9 and 55.0 and above), which were drawn from the wider 2.0 to 10.0 ng/mL range. phi has been approved in the United States, Europe and Australia (Loeb 2014). In the AUA 2026 guideline, phi is listed among serum add-on tests for men with a mildly raised PSA, and in one study of men with a prior negative biopsy, adding phi raised the negative predictive value of MRI for grade group 2 or higher cancer from 78% to 95%. Results apply only to the manufacturer's assays: samples in the pivotal study were processed within 8 hours and frozen, and Mayo asks for refrigeration within 3 hours.
LOINC 97150-7 (primary). Specimen: calculated.
Sources
- P2PHI - Overview: [-2]Pro Prostate Specific Antigen with Prostate Health Index, Serum, Mayo Clinic Laboratories
- PHI11 - Overview: Prostate Health Index Reflex, Serum, Mayo Clinic Laboratories
- A multicenter study of [-2]pro-prostate specific antigen combined with prostate specific antigen and free prostate specific antigen for prostate cancer detection in the 2.0 to 10.0 ng/ml prostate specific antigen range, The Journal of Urology (2011)
- The Prostate Health Index: a new test for the detection of prostate cancer, Therapeutic Advances in Urology (2014)
- Early Detection of Prostate Cancer: AUA/SUO Guideline (2023, amended 2026), American Urological Association (2026)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.