title: The effects of analytical factors on second trimester risk estimations.
abstract: OBJECTIVE
  Triple test with measured maternal serum alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol combination as a routine procedure for fetal Down's syndrome, trisomy 18 and neural tube defect screening has some intrinsic problems, such as precision. The aim of this study was to evaluate the effect of analytical variation of triple test on prenatal risk estimation.
  
  
  METHODS
  Five different serum pools were prepared and triple test was performed seven times for within run and five times for between run precision determination.
  
  
  RESULTS
  Within run and between run, precision values of risk estimations by measuring the same sample for Triple test were calculated to be 7.9-21.4% and 14.1-31.0% for trisomy 21, 13.2-23.7% and 14.2-15.1% for trisomy 18, 47.2 and 42.0 % for neural tube defect, respectively.
  
  
  CONCLUSIONS
  These results demonstrated that analytical variations have great impact on second trimester risk estimation procedures; therefore, triple test analyses should be carried out in laboratories using strict internal and external quality control programs. Moreover, triple test results should always be interpreted by considering analytical and biological variations.
authors.affiliation: Department of Clinical Chemistry, Gulhane Military Medical Academy, Ankara, Turkey. maserdar@gata.edu.tr
authors.forename: M A
authors.initials: MA
authors.lastname: Serdar
authors.forename: L
authors.initials: L
authors.lastname: Tütüncü
authors.forename: A
authors.initials: A
authors.lastname: Olgun
authors.forename: A
authors.initials: A
authors.lastname: Haşimi
authors.forename: T
authors.initials: T
authors.lastname: Ozgurtaş
authors.forename: M K
authors.initials: MK
authors.lastname: Erbil
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D006063:Chorionic Gonadotropin / Q000032:analysis; D002902:Chromosomes, Human, 16-18; D004314:Down Syndrome / Q000175:diagnosis*; D004964:Estriol / Q000032:analysis; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D008403:Mass Screening; D009436:Neural Tube Defects / Q000175:diagnosis*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D011262:Pregnancy Trimester, Second; D014314:Trisomy / Q000175:diagnosis*; D000509:alpha-Fetoproteins / Q000032:analysis
chemical_list: D015415:Biomarkers; D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins; D004964:Estriol