title: Assessment of free fetal DNA concentration in maternal plasma during the first trimester of pregnancy: comparative study between EDTA and PPT tubes - pilot study.
abstract: OBJECTIVE
  To compare ethylenediamine tetraacetic acid (EDTA) tubes and plasma preparation tubes (PPT) for evaluating maternal plasma during the first trimester of pregnancy.
  
  
  METHODS
  A cross-sectional study was conducted on 24 male fetuses in women between 6 and 14 weeks of pregnancy. Blood samples (10 mL) were collected and stored in EDTA and PPT tubes. Subsequently, the samples were centrifuged and sent for free fetal DNA extraction by means of the polymerase chain reaction (PCR) technique. The reactions were performed in a real time PCR machine for detecting the amplification products. The genome region chosen for performing the PCR reactions was a target specific for the Y chromosome, in which the DYS-14 marker was amplified only when the DNA was of male sex. The free fetal DNA concentration was given by the threshold cycle (TC). To compare the tubes, the paired Student t-test was used.
  
  
  RESULTS
  The mean gestational age was 11.08 ± 2.30 weeks (range: 6-14). The mean TC for PPT was 30.08 ± 1.05 (range: 27.08-32.61) and for EDTA, 30.23 ± 0.96 (range: 28.01-32.09), but without statistical significance (p=0.357).
  
  
  CONCLUSIONS
  We did not observe any statistically significant difference in free fetal DNA concentration between the EDTA and PPT tubes.
authors.affiliation: Department of Obstetrics and Gynecology, Medical College Sciences of Santa Casa of São Paulo (FCMSCSP) , São Paulo-SP , Brazil .
authors.forename: Carolina Schneider
authors.initials: CS
authors.lastname: Chadud
authors.forename: Edward
authors.initials: E
authors.lastname: Araujo Júnior
authors.forename: Ciro Dresh
authors.initials: CD
authors.lastname: Martinhago
authors.forename: Viviane Cristina Mello
authors.initials: VC
authors.lastname: Andari
authors.forename: Giselle Darahem
authors.initials: GD
authors.lastname: Tedesco
authors.forename: Luiz Claudio Silva
authors.initials: LC
authors.lastname: Bussamra
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Aoki
mesh_terms: D000925:Anticoagulants / Q000494:pharmacology*; D001793:Blood Preservation / Q000379:methods*; D001800:Blood Specimen Collection / Q000379:methods*; D018797:Cell Cycle Proteins / Q000032:analysis / Q000235:genetics; D003430:Cross-Sectional Studies; D004247:DNA / Q000032:analysis / Q000097:blood*; D004492:Edetic Acid / Q000494:pharmacology*; D005260:Female; D005333:Fetus / Q000378:metabolism*; D005865:Gestational Age; D006801:Humans; D008297:Male; D010865:Pilot Projects; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood* / Q000235:genetics
chemical_list: D000925:Anticoagulants; D018797:Cell Cycle Proteins; C497749:TSPY1 protein, human; D004247:DNA; D004492:Edetic Acid
keywords: EDTA; PCR; PPT; first trimester of pregnancy; free fetal DNA