What is the PHI test?

The PHI test is a new blood test that may eventually replace the PSA test when testing for prostate cancer. It is a simple, noninvasive blood test that is three times more specific than PSA in detecting prostate cancer. Controversy remains surrounding the use of the PSA test to screen for prostate cancer. This is due to the belief that the PSA test may lead to over-diagnosis and over-treatment in men with low-grade, less aggressive forms of the disease. 

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The PSA test is also not specific to prostate cancer and as a result, many men often have unnecessary biopsies. Prostate cancer diagnoses are on the rise, and the disease remains the second most common cancer in American men as well as the second leading cause of cancer deaths.

The PSA test is not specific for prostate cancer. There are several other possibilities as to why your PSA may be elevated including an enlarged prostate, prostatitis, inflammation, or a urinary tract infection. But when the PSA is above 4.0 ng/ml, or is “abnormal”, and other possible causes have been ruled out, the next step for the patient is to have a prostate biopsy. If prostate biopsy is negative, but the PSA is still high, the patient usually has to have a repeat biopsy every six months or year. 

There are about 1.5 million prostate biopsies each year and about 25 million men have had at least one negative biopsy. The PHI test improves the diagnosis of prostate cancer by using three different prostate specific markers, which makes the test three times more specific for prostate cancer compared to the current PSA test. The test gives doctors a more accurate picture in regards to what an elevated PSA level indicates as well as the probability of finding cancer on a prostate biopsy.

The PHI test measures total PSA as well as two special forms of the protein: free PSA (fPSA), and pro2PSA. tPSA includes all types of PSA circulating in the bloodstream, whether free or bound to other proteins; fPSA is PSA that circulates as a free protein, unattached to any other proteins; and pro2PSA is a form of PSA that is highly expressed in prostate cancer tissue and is associated with more aggressive disease. Using these three values, a PHI score is calculated. The PHI score provides a more accurate measurement to assess prostate cancer risk than any known PSA-based marker alone. And by using pro2PSA, the PHI test can detect more aggressive cancers. This reduces the harm many men experience with overtreatment.