Stability of first trimester placental growth factor in serum and whole blood

Background Placental growth factor (PlGF) is a proposed first-trimester screening marker for pre-eclampsia. This study investigates the stability of PlGF in serum and whole blood at typical routine storage temperatures. Methods Serum pools were stored at refrigerator temperature, room temperature or 30 degrees C for up to 30 days, or exposed to up to six freeze-thaw cycles. Whole blood was stored at room temperature or 30 degrees C for up to 6 days. PlGF was quantified using a DELFIA Xpress analyser. Results Placental growth factor levels increased over time, seemingly because of the dissociation of PlGF bound to a soluble binding protein, sFlt-1. Increase was slow in serum at refrigerator temperature, remaining stable (less than 10% change from start point) for at least 30 days. At room temperature PlGF was stable for 3.3 days and at 30 degrees C for 1 day. Serum PlGF remained stable for at least six freeze-thaw cycles. In whole blood, instability was worse, being stable for only 19.4 h at room temperature and just 3.3 h at 30 degrees C. Conclusion Routine screening of sample handling requires careful monitoring. However, no extra precautions need to be taken when PlGF is used for pre-eclampsia screening run alongside existing first trimester aneuploidy screening programs that include hCG. Copyright c 2011 John Wiley & Sons, Ltd.