Prostate Health Index (phi) [Test in Focus]

Useful For

  • Assessing the patient’s probability of having detectable prostate cancer when total
    prostate specific antigen (PSA) concentrations are between 4–10 ng/mL.
  • Results from a prospective, multicenter clinical trial found that phi provides better risk stratification and reduces unnecessary biopsies by 30%, which reduces medical costs and time for the patient.1

Video Overview

Clinical Information

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 (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.

Prostatic biopsy is required for diagnosis of cancer.

Specimen Information

Specimen Type

  • Serum Red

Specimen Required

  • Patient Preparation: Specimens for testing should be drawn prior to prostate manipulations such as digital rectal examination (DRE), prostatic massage, transrectal ultrasound (TRUS), and prostatic biopsy.
  • Collection Container/Tube: Red top
  • Submission Container/Tube: Plastic vial
  • Specimen Volume: 1 mL
  • Collection Instructions: Spin down within 3 hours of draw and separate serum from cells.

Performance Information

Day(s) and Time(s) Test Performed

  • Monday through Friday; 6 a.m.-12 a.m.
  • Saturday; 6:30 a.m.-5 p.m.

Analytic Time

  • 1 day
1. Loeb S, Martin S, Broyles, D, et al. The Prostate Health Index (phi) Selectively Identifies Clinically Significant Prostate Cancer. J. Urology, Jan. 2015.

Mayo Clinic Laboratories

This post was authored by the Marketing Team at Mayo Clinic Laboratories.