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From the Spring 2015 Quest

Dr. Catalona and other researchers investigated whether the Prostate Health Index (phi) test improved specificity for detecting clinically significant prostate cancer to help reduce prostate cancer overdiagnosis. The team compared the performance of PSA, percent-free PSA, [-2]proPSA and phi in 658 men age 50 years or older. These men all had a PSA between 4-10 ng/ml, normal digital rectal examination and a prostate biopsy. The study found that phi scores were significantly higher in men with Gleason 7 or greater cancer. At the 90% sensitivity cut point for phi (a score less than 28.6), 30.1% of patients could have been spared an unnecessary biopsy for benign or insignificant prostate cancer, compared to 21.7% when using percent-free PSA.

Loeb S., et al. The Prostate Health Index Selectively Identifies Clinically Significant Prostate Cancer. J Urol. 2014 Nov 15. pii: S0022- 5347(14)04900-3. doi: 10.1016/j.juro.2014.10.121. [Epub ahead of print]
The Prostate Health Index (phi) is a new test combining total, free and [-2]proPSA into a single score. It is calculated using the following formula: ([-2]proPSA/free PSA) x √PSA. Intuitively, this formula makes sense, in that men with a higher total PSA and p2PSA with a lower free PSA are more likely to have clinically significant prostate cancer. The phi test was recently approved by the FDA and is available in the U.S., Europe and Australia.
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