Risk-based prenatal screening for trisomy 18 using alpha-fetoprotein,unconjugated oestriol and human chorionic gonadotropin |
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Authors: | Glenn E Palomaki BS James E Haddow George J Knight Nicholas J Wald Anne Kennard Jacob A Canick Devereux N Saller Jr Miriam G Blitzer Lois H Dickerman Rachel Fisher Dagmar Hansmann Manfred Hansmann David A Luthy Anne M Summers Philip Wyatt |
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Institution: | 1. Foundation for Blood Research, Scarborough, ME 04074, U.S.A.;2. Wolfson Institute of Preventive Medicine, London, EC1N 6BQ, U.K.;3. Women and Infants Hospital, Providence, RI 02905, U.S.A.;4. University of Maryland, Baltimore, MD 21201, U.S.A.;5. Center for Human Genetics and Case Western Reserve, University Hospitals, Cleveland, OH 44106, U.S.A.;6. Michigan State University, East Lansing, MI 48824, U.S.A.;7. Department of Prenatal Diagnosis and Therapy, University of Bonn, Bonn, Germany;8. Swedish Hospital Medical Center, Seattle, WA 98104, U.S.A.;9. North York General Hospital, North York, Ontario M2K1E1, Canada |
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Abstract: | Nine centres collaborated to examine the feasibility of a screening method for trisomy 18 that was based on assigning individual risk, using a combination of maternal age and measurements of alpha-fetoprotein (AFP), unconjugated oestriol (uE3), and human chorionic gonadotropin (hCG). Second-trimester measurements of these analytes were obtained from 94 trisomy 18 pregnancies. In the 89 pregnancies without an associated open defect, the median levels for AFP, uE3, and hCG were 0.65, 0.43 and 0.36 multiples of the unaffected population median, respectively. The strongest individual predictor of risk for trisomy 18 was uE3, followed by hCG, AFP, and maternal age, in that order. Using a method of individual risk estimation that is based on the three markers and maternal age, 60 per cent of pregnancies associated with trisomy 18 would be detected at a risk cut-off level of 1:100, with a false-positive rate of about 0.2 per cent. One in nine pregnancies identified as being at increased risk for trisomy 18 would be expected to have an affected pregnancy. This risk-based screening method is more efficient than an existing method that is based on fixed analyte cut-off levels. Even though the birth prevalence of trisomy 18 is low, prenatal screening can be justified when performed in conjunction with Down syndrome screening and when a high proportion of women offered amniocentesis have an affected fetus. |
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Keywords: | trisomy 18 prenatal screening alpha-fetoprotein human chorionic gonadotropin unconjugated oestriol |
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