Prostate Health Index (phi) [A Test in Focus]
- 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
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.
- Serum Red
- 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.
Day(s) and Time(s) Test Performed
- Monday through Friday; 6 a.m.-12 a.m.
- Saturday; 6:30 a.m.-5 p.m.
- 1 day