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Antenatal screening for chromosomal abnormalities

  • US 6,010,912 A
  • Filed: 12/04/1995
  • Issued: 01/04/2000
  • Est. Priority Date: 11/28/1992
  • Status: Expired due to Term
First Claim
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1. A method for antenatal screening for a chromosomal abnormality in a fetus, comprising:

  • A) calculating a pregnant patient'"'"'s a priori risk of carrying a fetus having said chromosomal abnormality,B) measuring said pregnant patient'"'"'s blood in the first trimester for a concentration of free beta hCG, its precursors and metabolites, or a mixture thereof,C) measuring said pregnant patient'"'"'s blood in the first trimester for a concentration of pregnancy associated plasma protein A, its precursors and metabolites, or a mixture thereof,D) calculating a normalized value for each of said concentrations from steps B) and C) by dividing said concentrations by a median value found in a population of women with unaffected pregnancies and same gestational age as said pregnant patient,E) calculating a first probability that the normalized values are part of a bivariate Gaussian distribution of values found in pregnancies with said chromosomal abnormality,F) calculating a second probability that the normalized values are a part of a bivariate Gaussian distribution of values found in unaffected pregnancies,G) calculating a likelihood ratio, said likelihood ratio being the ratio of said first probability and said second probability, andH) modifying the a priori risk by the likelihood ratio.

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