The p2PSA ([-2] isoform of proenzyme PSA) can improve the separation of benign prostate hypertrophy from early prostate cancer (negative digital rectal exam and total PSA 2.5 to 10 ng/ml).
Method: Hybritech assays on the Beckman Coulter Access
Parameters:
(1) total PSA in ng/mL
(2) p2PSA in ng/mL (or ng/L)
(3) free PSA in ng/mL
percent p2PSA =
= (p2PSA in ng/mL) / (free PSA in ng/mL) * 100%
phi =
= (p2PSA in ng/L) / (free PSA in ng/mL) * SQRT(total PSA in ng/mL)
where:
• The units for p2PSA for one equation is ng/mL for one calculation and ng/L for the second.
The median phi for a patient with prostate cancer was around 35.
The median phi for a patient without prostate cancer was around 26.
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