FRIDAY, Feb. 2 (HealthDay News) -- Free fetal DNA can be distinguished from maternal DNA in maternal plasma using single nucleotide polymorphisms, according to a study published online Feb. 2 in The Lancet. The technique could be used in a diagnostic test for chromosomal abnormalities such as trisomy 21.
Ravinder Dhallan, M.D., of Ravgen, Inc. in Columbia, Md., and colleagues conducted a study of blood samples taken from 60 pregnant women, calculated the proportion of free fetal DNA and used single nucleotide polymorphisms to distinguish it from maternal DNA.
Among the 60 samples there was a mean 34 percent proportion of free fetal DNA, and while 57 samples produced a normal result, three revealed abnormal DNA ratios for chromosome 13 and chromosome 21. When the same women underwent amniocentesis or when the babies were born, the non-invasive test was found to have generated one false-positive and one false-negative result, the equivalent of a 66.7 percent positive predictive value and a 98.2 percent negative predictive value.
"Our results show that single nucleotide polymorphisms can be used to distinguish fetal DNA from maternal DNA -- and to determine the copy number of fetal chromosomes -- in maternal blood samples," the authors conclude. "With further refinement, a prenatal diagnostic test based on the methods described could be a useful complement to currently available prenatal tests."
Several authors are employees and/or stockholders at Ravgen, Inc., the company that has issued a patent for the method described in this study.
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