FDA approves Beckman Coulter’s “Prostate Health Index” test


According to a media release from Beckman Coulter and a report on the MedPage Today web site, the U.S. Food and Drug Administration has approved marketing of the “Prostate Health Index” test as a new way to test for risk of prostate cancer.

The Prostate Health Index or phi test combines information from levels of total PSA, free PSA, and a PSA precursor protein known as [-2]pro-PSA. The company claims that this test is “2.5 times more specific in detecting prostate cancer than PSA (prostate-specific antigen) in patients with PSA values in the 4-10 ng/mL range and is proven to reduce the number of prostate biopsies.” However, the utility of this test in clinical practice is still to be clearly demonstrated.

Like the PCA3 test, the phi test will presumably be a test used exclusively by urologists and a few other specialists in an attempt to better identify those men who are at risk for prostate cancer after an initial PSA test. If the use of this test can really reduce the number of prostate biopsies by something like 30 percent (as claimed by Beckman Coulter), then certainly it does have a very real value for this reason alone. What is not at all clear at present is whether this test can offer any meaningful assistance in helping to differentiate between clinically significant prostate cancer that needs treatment and prostate cancer that can simply be monitored under active surveillance.

6 Responses

  1. Here is what I don’t understand about any blood test that is not 100% PCa specific. Yea, I know none are, at least for pre-RRP people.

    How can they arrive at the conclusion this test reduces the “need for prostate biopsyies by 30%” or any other amount for that matter? To me the only way to definitively determine that someone does not have PCa is to remove his prostate and examine it after whatever test you run on them. Of which I am sure that they did not do to everyone in this study.

    So, what was the creiteria used to determine that 30% of the people that were biopsied did not need to be? Was this conclusion simply made as a result of a negative biospies over a period of time from the people who fell into a certain range of results from this test?

    To be truly comfortable with this result I would want to follow people for a long period of time. You know like 15-25 years before I would draw any conclusions from the results of this “screening method.” To me this is just more “shooting in the dark” really.

    I guess it’s as good as science can do right now, not saying I could do any better……

  2. Chris:

    The studies that were done to approve this test were all based on blood samples and tissue specimens from patients who had had prior biopsies and surgery and on negative biopsy controls. In other words, there has never been a prospective trial of the phi test (that I am aware of). What the studies done do show, however, is that there was a correlation between the phi scores and the probabilities of positive and negative biopsies and the subsequent surgical findings among the men who went on to have RPs.

    I think that you are correct and that to really “prove” the value of the phi test, we need long-term prospective data, and I would like to think that Becton Coulter will fund an appropriate long-term, prospective registry study of some type. Of course whether they will be willing to do that is something you would need to ask them.

    The other issue that is important here is that having some cancer in one’s prostate is not the same as having clinically significant prostate cancer. We all know that somewhere between 25 and 40% of all the men who get diagnosed today would probably never have known about or suffered from clinically significant prostate cancer if they hadn’t been diagnosed as a consequence of a PSA test and a biopsy. So the real question here is whether this test will help not to diagnose the men who don’t need to be diagnosed just as much as it is whether it will help to diagnose those men who do need to be diagnosed.

  3. Mike,

    Wasn’t the PCA3 study also aimed at post-biopsy men to estabish whether another biopsy was essential?

    As far as I know there never was a study of PCA3 v PSA — two non-prostate cancer-specific tests to see if one was truly better.

    And since both the PCA3 and phi use PSA as part of their formula, surely all the PSA-specific issues regarding unattributable rises, etc., would be imported into these tests?

  4. Terry:

    The major study which was the basis for the approval of the PCA3 test was indeed focused on the use of PCA3 as a test to indicate the need for further biopsy in men who showed continuing signs of risk for prostate cancer after and initial negative biopsy. That study did, in part, compare the value of the PCA3 test to the PSA test alone in these men.

    As far as I am aware there has never been a direct comparison of the PCA3 test to the total PSA test in undiagnosed men who have never previously received a prostate biopsy.

    With respect to the fact that the phi test does indeed incorporate all of the inherent problems associated with the total PSA and %Free PSA tests … please don’t get me started!

  5. Here is a link to an an earlier, more detailed article on phi and [-2]pro-PSA:

  6. Here is the formula used for the phi test:

    phi = p2PSA/fPSA * √PSA

    Obviously, the higher the p2PSA and PSA and the lower the fPSA, the higher the chances that we are dealing with prostate cancer. Note that the PSA is represented with the square root; therefore, phi is much more sensitive to p2PSA than it is to PSA.

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