The stability of free‐β human chorionic gonadotrophin and pregnancy‐associated plasma protein‐A in first trimester dried blood spots

Abstract

To determine the stability of first trimester free-β human chorionic gonadotrophin (free-β hCG) and pregnancy-associated plasma protein-A (PAPP-A) in dried blood spots (DBSs) under typical storage conditions. First trimester maternal blood was spotted onto filter paper and left to dry. DBSs were analysed for PAPP-A and free-β hCG using an AutoDELFIA dual assay at t = 0. Cards were stored at one of - 20 °C, refrigerator temperature, room temperature or 30 °C and reanalysed at set future time points. Free-β hCG was stable (<10% change in concentration) under all temperatures tested for at least 35 days. PAPP-A was stable at - 20 °C and refrigerator temperature for at least 35 days. However, PAPP-A levels decreased by 10% at 4.1 days at room temperature and at 3.9 days at 30 °C. Longer-term storage at - 20 °C and refrigerator temperature showed that both PAPP-A and free-β hCG levels were significantly decreased by 107 and 244 days. Free-β hCG stability is greatly improved in DBS compared to serum storage; however PAPP-A stability is decreased in the DBS medium. Despite this DBS, screening may not necessitate such strict storage and transportation rules compared to serum screening programmes.