title: PAPP-A and free ss-hCG stability in first trimester serum using PerkinElmer AutoDELFIA and DELFIA Xpress systems.
abstract: BACKGROUND
  In this study we aim to investigate the stability of free-beta-hCG and PAPP-A over time in serum and whole blood in typical routine temperatures.
  
  
  METHODS
  Serum pools were stored under the following temperatures: 30 degrees C, room temperature, refrigerator temperature and -20 degrees C, for up to 240 days. Stability of the markers in whole blood was examined in a shorter study and compared to serum. Samples were analysed using the AutoDELFIA and DELFIA Xpress analysers.
  
  
  RESULTS
  On the AutoDELFIA, considering a 10% change acceptable, PAPP-A levels are stable in serum for 142 days at refrigerator temperature, 37 days at room temperature and 20 days at 30 degrees C. Free-beta hCG is stable in serum for 94 days at refrigerator temperature, 3 days at room temperature and 12 h at 30 degrees C. There was no significant change with either analyte after -20 degrees C storage for up to 240 days or after six repeated freeze-thaw cycles. In whole blood, free-beta hCG levels increased more rapidly compared to serum, especially at 30 degrees C.
  
  
  CONCLUSIONS
  Normal handling of samples is only likely to minimally effect the risk assessment of chromosomal anomalies. However, careful attention should be paid to minimise the increase of free-beta hCG levels in samples shipped as whole blood.
authors.affiliation: Prenatal Research Unit, Clinical Biochemistry Department, King George Hospital, Goodmayes, UK.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Cowans
authors.forename: Anastasia
authors.initials: A
authors.lastname: Stamatopoulou
authors.forename: Johanna
authors.initials: J
authors.lastname: Hellström
authors.forename: Minna-Maarit
authors.initials: MM
authors.lastname: Mäkelä
authors.forename: Kevin
authors.initials: K
authors.lastname: Spencer
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis*; D055550:Protein Stability; D013048:Specimen Handling; D013696:Temperature
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A