title: The assessment of combined first trimester screening in women of advanced maternal age in an Asian cohort.
abstract: BACKGROUND
  First trimester screening (FTS) is a validated screening tool that has been shown to achieve detection rates of 84%-90% for trisomies 21, 18 and 13. However, its effectiveness for different maternal ages has not been assessed. The present study aimed to assess the performance of FTS in an Asian population, and to compare its effectiveness in older (≥ 35 years) and younger (< 35 years) women. The potential use of noninvasive prenatal test (NIPT) as a contingent screening test is also examined.
  
  
  METHODS
  Data on cases of FTS performed on singleton pregnancies over a six-year period was collated from two Singapore maternal centres, National University Hospital and Singapore General Hospital. Cases that had a 1:250 risk of trisomy were considered to be screen-positive. Pregnancy outcomes were obtained from birth records or karyotype test results.
  
  
  RESULTS
  From 10,289 FTS cases, we obtained a sensitivity of 87.8%, a specificity of 97.6%, a false positive rate of 2.4% and a false negative rate of 0.06% for the detection of aneuploidy. The overall detection rate for trisomy 21 was 86.5%-85.7% for older women and 87.5% for younger women. The mean number of invasive tests required per case of trisomy 21 was 9.3 in younger women, 8.6 in older women and 13.5 in women with intermediate risk (1:250-1,000).
  
  
  CONCLUSIONS
  While the performance of FTS was similar in younger and older women, more invasive procedures were required to diagnose trisomy 21 in women with intermediate risk. It may be advantageous to offer contingent NIPT to this group of women to reduce the risk of iatrogenic fetal loss.
authors: Sarah Weiling
authors: SW
authors: Li
authors: Angela Natalie
authors: AN
authors: Barrett
authors: Leena
authors: L
authors: Gole
authors: Wei Ching
authors: WC
authors: Tan
authors: Arijit
authors: A
authors: Biswas
authors: Hak Koon
authors: HK
authors: Tan
authors: Department of Obstetrics and Gynaecology, National University of Singapore, NUHS Tower Block, Level 12, 1E Kent Ridge Road, Singapore 119228. obgmac@nus.edu.sg.
authors: Mahesh
authors: M
authors: Choolani
mesh_terms: D000293:Adolescent; D000328:Adult; D000782:Aneuploidy; D001208:Asia; D015331:Cohort Studies; D004247:DNA / Q000032:analysis; D004314:Down Syndrome / Q000175:diagnosis; D005260:Female; D006801:Humans; D007621:Karyotyping; D008423:Maternal Age; D062145:Maternal Serum Screening Tests / Q000379:methods*; D008875:Middle Aged; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011296:Prenatal Diagnosis / Q000379:methods*; D012307:Risk Factors; D012846:Singapore; D014314:Trisomy / Q000175:diagnosis
chemical_list: D004247:DNA
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