Pre-analytical in-vitro stability of [-2]proPSA in blood and serum

Objectives: [-2]proPSA may discriminate prostate cancer from benign biopsy results. We characterized the pre-analytical stability of [-2]proPSA. Design and methods: 22 volunteers, total PSA of 4.5-19.3 mu g/L, had blood drawn simultaneously. Baseline measurements were performed and samples were stored under various conditions prior to measurements. Freeze-thaw cycles were performed. [-2]proPSA was measured with the p2PSA automated research use only immunoassay on the Access analyzer. Results: Mean [-2]proPSA increases with clotting time, exceeding 10% change in recovery after 3 h. In serum, [-2]proPSA values decline over time under investigated storage conditions. Serum samples kept frozen show less than 10% variation in recoveries over the course of 2 freeze-thaw cycles. Conclusions: For proper measurement of [-2]proPSA, blood samples should be centrifuged within 3 h of blood draw. Serum may be stored at RT or refrigerated (+4 degrees C) for a maximum of 48 h and should be frozen if stored for a longer period. Two freeze-thaw cycles have no effect on [-2]proPSA stability. (c) 2010 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.