FRIDAY, June 8 (HealthDay News) -- A noninvasive method involving chromosome-selective sequencing of cell-free DNA (cfDNA) and assessment of individual risk detects trisomy 18 and 21 with high sensitivity, according to a study published online June 4 in the American Journal of Obstetrics & Gynecology.

Mary E. Norton, M.D., from Stanford University/Lucile Packard Children's Hospital in California, and colleagues conducted a multicenter cohort study involving analysis of cfDNA from maternal plasma. Aneuploidy risk (high risk or low risk) was reported for each subject following chromosome-selective sequencing on chromosomes 18 and 21.

Of the 81 trisomy 21 cases, the researchers classified all 81 as high risk for trisomy 21. There was one false positive in 2,888 normal cases, for an overall sensitivity of 100 percent and a 0.03 percent false-positive rate. Thirty-seven of the 38 cases of trisomy 18 were classified as high risk and two false positives were seen among the 2,888 normal cases, for a sensitivity of 97.4 percent and a false-positive rate 0.07 percent.

"Chromosome-selective sequencing of cfDNA and application of an individualized risk algorithm is effective in the detection of fetal trisomy 21 and trisomy 18," the authors write.

Several authors are employed by or have other financial ties to Ariosa Diagnostics, which funded the study.

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