title: The stability of free-β human chorionic gonadotrophin and pregnancy-associated plasma protein-A in first trimester dried blood spots.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Clinical Biochemistry, King George Hospital, Goodmayes, Essex, UK.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Cowans
authors.forename: Anastasia
authors.initials: A
authors.lastname: Stamatopoulou
authors.forename: Paivi
authors.initials: P
authors.lastname: Liitti
authors.forename: Mikko
authors.initials: M
authors.lastname: Suonpaa
authors.forename: Kevin
authors.initials: K
authors.lastname: Spencer
mesh_terms: D001800:Blood Specimen Collection / Q000009:adverse effects / Q000379:methods*; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood / Q000378:metabolism*; D003890:Desiccation / Q000379:methods; D005260:Female; D006801:Humans; D009994:Osmolar Concentration; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood* / Q000378:metabolism; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis / Q000378:metabolism*; D011296:Prenatal Diagnosis / Q000379:methods*; D055550:Protein Stability; D013696:Temperature; D013997:Time Factors
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A