Sequencing All 24 Human Chromosomes Uncovers Rare Disorders

Extending noninvasive prenatal screening to all 24 human chromosomes can detect genetic disorders that may explain miscarriage and abnormalities during pregnancy, according to a study by researchers at NIH and other institutions. Because of the way data have been analyzed, typical genomic tests performed during pregnancy have targeted extra copies of chromosomes 21, 18 and 13, but rarely evaluated all 24 chromosomes. The study findings, which appeared in the Aug. 30 issue of Science Translational Medicine, may ultimately improve the accuracy of these tests, including by explaining why some give false-positive results.

Women often request noninvasive screening tests to detect genetic conditions. These tests, however, typically focus only on Down syndrome and other common trisomies. A trisomy is a condition in which there are three instances of a certain chromosome instead of the standard two.

“Extending our analysis to all chromosomes allowed us to identify risk for serious complications and potentially reduce false-positive results for Down syndrome and other genetic conditions,” said Dr. Diana Bianchi, senior author of the study and chief of NHGRI’s prenatal genomics and therapy section. She is also NICHD director.