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 °C for up to 30 days, or exposed to up to six freeze-thaw cycles. Whole blood was stored at room temperature or 30 °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 °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 °C.


CONCLUSIONS
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 hCGβ.
Department of Clinical Biochemistry, King George Hospital, Goodmayes, Essex, UK.
N J
NJ
Cowans
H
H
Alfthan
U H
UH
Stenman
K
K
Spencer
D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D008403:Mass Screening; D000072483:Placenta Growth Factor; D011225:Pre-Eclampsia / Q000175:diagnosis*; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000097:blood*; D011261:Pregnancy Trimester, First; D055550:Protein Stability; D012044:Regression Analysis
D015415:Biomarkers; C000608036:PGF protein, human; D011257:Pregnancy Proteins; D000072483:Placenta Growth Factor