title: The influence of different sample collection types on the levels of markers used for Down's syndrome screening as measured by the Kryptor Immunosassay system.
abstract: BACKGROUND
  In a rapid point-of-care screening programme for chromosomal anomalies, analysis of biochemical markers in maternal blood can now be accomplished in a rapid time frame (less than 20 min). The need to leave whole blood samples some 10 min for coagulation and a further 5 min for centrifugation adds additional processing time.
  
  
  METHODS
  The possibilities for reducing this processing time were investigated using various anticoagulated blood collection systems and the Kryptor analytical platform. Plasma levels of alpha-fetoprotein (AFP), pregnancy-associated plasma protein-A (PAPP-A) and free human chronic gonadotrophin beta-subunit (beta-hCG) were compared with those in maternal serum.
  
  
  RESULTS
  From the mean results from ten patients it was shown that use of heparin plasma resulted in a statistically significant reduction in levels of PAPP-A and that EDTA plasma reduced the levels of PAPP-A dramatically. For AFP, levels in citrated plasma and EDTA plasma were also significantly reduced, whereas levels of free beta-hCG were not affected.
  
  
  CONCLUSIONS
  Use of alternative sample types for PAPP-A is not possible. The sample of choice for first trimester screening using the Kryptor platform is maternal serum.
authors.affiliation: Clinical Biochemistry Department, Harold Wood Hospital, Gubbins Lane, Romford RM3 0BE, UK. KevinSpencer1@aol.com
authors.forename: Kevin
authors.initials: K
authors.lastname: Spencer
mesh_terms: D002624:Chemistry, Clinical / Q000379:methods; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D002869:Chromosome Aberrations; D004314:Down Syndrome / Q000175:diagnosis* / Q000235:genetics*; D005260:Female; D005819:Genetic Markers; D006801:Humans; D008403:Mass Screening / Q000379:methods; D011247:Pregnancy; D011266:Pregnancy-Associated Plasma Protein-A / Q000096:biosynthesis; D011296:Prenatal Diagnosis / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000509:alpha-Fetoproteins / Q000096:biosynthesis
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D005819:Genetic Markers; D000509:alpha-Fetoproteins; D011266:Pregnancy-Associated Plasma Protein-A