The Prostate Health Index (phi) is a test that utilizes the combination of three blood tests to produce a "phi score." The test was designed for men who have a PSA between 4 and 10 ng/ml. Research has shown that phi provides more accurate information than PSA alone at determining which individuals may need a prostate biopsy and which individuals have an elevated PSA that is more likely due a benign condition, such as normal prostate growth, or an infection in the prostate.
Probability of Prostate Cancer on Biopsy for Beckman Coulter: This section describes several different phi result ranges and the approximate probability that individuals in this range would have some form of prostate cancer upon biopsy. As an example, the first column (Beckman Coulter phi Range) shows 0 - 26.9. This means that men with a phi score of 0 - 26.9 have a 9.8% probability of having prostate cancer should they receive a biopsy (second column). The 95% confidence interval shows the approximate range of the probability of cancer, and means that 95% of men with a phi between 0 and 26.9 have a probability of having prostate cancer on biopsy between 5.2% (low end of the scale) to 15.4% (high end of the scale).
Prostate Health: This section describes the 4 different tests that make up the phi score components. Below you will find a description of each of these tests and what they mean
PSA: PSA (prostate specific antigen) is a protein that is produced by prostate cells. In this case, PSA represents Total PSA, which is the PSA that is bound to other proteins as well as PSA that is found on its own in the blood. The PSA that is found on its own is known as PSA Free.
% Free PSA: This is the PSA Free divided by the PSA bound to other proteins (and the approximate percentage that this constitutes).
p2PSA: This is a test that measures the amount of -2 pro PSA in the blood, a special type of free floating (unbound to other proteins) PSA which has been shown in research to be present in higher concentration when cancer is present (as opposed to Total PSA, which can be elevated in the presence of benign conditions such as an enlarged prostate or a prostate infection).
phi: phi (Prostate Health Index) constitutes a special calculation (score) between the 3 markers above (PSA, PSA Free, and p2PSA). It is with this calculation that your individual probability of having prostate cancer is determined and if further tests (such as a biopsy) may be necessary.