Stability of [-2]Pro-PSA in whole blood and serum: analysis for optimal measurement conditions

Background: The clinical usefulness of [-2]pro-PSA (where PSA is prostate-specific antigen) in prostate cancer diagnosis has been emphasized in recent studies. To determine proper blood sample handling conditions for [-2]pro-PSA evaluation, we analyzed the preanalytical stability of [-2]pro-PSA.

Methods: Blood samples from 22 Japanese males were stored under various conditions before total PSA (tPSA), free PSA, and [-2]pro-PSA concentrations were measured, and the preanalytical stability of [-2]pro-PSA and the changes in the Prostate Health Index (phi) were assessed.

Results: [-2]Pro-PSA was stable in serum for at least 24 hr at both room temperature (RT) and at 4°C. However, [-2]pro-PSA levels in whole blood increased rapidly over time, particularly at RT. Mean recovery (%) of [-2]pro-PSA in whole blood at RT was >110% at 1 hr after drawing of blood. The phi tended to increase over time in a pattern similar to the change in[-2]pro-PSA.

Conclusions: Preanalytical stability was lower for [-2]pro-PSA than for free PSA or tPSA. Whole-blood [-2]pro-PSA increased in a time-dependent manner, particularly at RT. Thus, whole blood samples collected at RT should be centrifuged within 1 hr after drawing. The [-2]pro-PSA in serum is stable for at least 24 hr at both RT and at 4°C.