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.