title: Analysis of first-trimester combined test results in preparation for a cell-free fetal DNA era.
abstract: OBJECTIVE
  To survey experience with the first-trimester combined test (FCT) for trisomy 21 (T21) in different risk score groups to determine the most useful clinical application of cell-free fetal DNA (cffDNA) screening.
  
  
  METHODS
  In a retrospective study, the records of FCT results obtained at a center in Turkey between January 2009 and January 2014 were reviewed. The FCT results and rates of uptake of invasive diagnostic testing were compared among different risk score groups.
  
  
  RESULTS
  FCT results were available for 4804 pregnancies; 276 (5.7%) had IDT results. Ten (72.7%) of 11 cases of T21 had a risk score of 1:300 or more. The IDT uptake rates were 54.5%, 51.9%, and 47.4% at risk scores of 1:100 or more, 1:200 or more, and 1:300 or more, respectively. In the group at intermediate risk (1:1001-1:3000), no pregnancy had an FCT result of both low pregnancy-associated plasma protein A and high free β-human chorionic gonadotropin, but 30 (3.9%) of 766 pregnancies had both advanced maternal age and high β-human chorionic gonadotropin.
  
  
  CONCLUSIONS
  cffDNA screening should be used to optimize IDT uptake in pregnancies with a risk score of 1:101-1:1000. The selective power of the FCT diminishes beyond the 1:1001 score and cffDNA screening cannot yet be recommended routinely.
authors: Department of Obstetrics and Gynecology, Dokuz Eylul University School of Medicine, Balcova, Izmir, Turkey. Electronic address: semirkose@yahoo.com.
authors: Semir
authors: S
authors: Kose
authors: Central Clinical Laboratory, University Hospital, Dokuz Eylul University School of Medicine, Balcova, Izmir, Turkey.
authors: Dilek
authors: D
authors: Cımrın
authors: Department of Obstetrics and Gynecology, Dokuz Eylul University School of Medicine, Balcova, Izmir, Turkey.
authors: Nuri
authors: N
authors: Yıldırım
authors: Department of Medical Genetics, Dokuz Eylul University School of Medicine, Balcova, Izmir, Turkey.
authors: Ozge
authors: O
authors: Aksel
authors: Department of Biostatistics, Dokuz Eylul University School of Medicine, Balcova, Izmir, Turkey.
authors: Pembe
authors: P
authors: Keskinoglu
authors: Department of Medical Genetics, Dokuz Eylul University School of Medicine, Balcova, Izmir, Turkey.
authors: Elcin
authors: E
authors: Bora
authors: Department of Medical Genetics, Dokuz Eylul University School of Medicine, Balcova, Izmir, Turkey.
authors: Tufan
authors: T
authors: Cankaya
authors: Department of Obstetrics and Gynecology, Dokuz Eylul University School of Medicine, Balcova, Izmir, Turkey.
authors: Sabahattin
authors: S
authors: Altunyurt
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000097:blood; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004247:DNA / Q000032:analysis; D004314:Down Syndrome / Q000097:blood / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008423:Maternal Age; D008875:Middle Aged; D048208:Nuchal Translucency Measurement / Q000379:methods; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood*; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis*; D011296:Prenatal Diagnosis / Q000379:methods*; D012189:Retrospective Studies; D014314:Trisomy / Q000175:diagnosis*; D014421:Turkey; D055815:Young Adult
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D004247:DNA; D011266:Pregnancy-Associated Plasma Protein-A
keywords: Cell-free fetal DNA; First-trimester combined test; Invasive diagnostic test; Noninvasive prenatal testing; Trisomy 21