Less expensive screening for chromosomal abnormalities

Reserving full karyotyping for the 10% of fetuses with first trimester nuchal translucency (NT) measurements of 4 mm or more and using quantitative fluorescent polymerase chain reaction (qf-PCR) for less suspicious samples may be an effective screening strategy that provides rapid results at significant cost savings, according to a recent observational study.

Researchers from the United Kingdom evaluated approximately 17,500 chorionic villus samples obtained after assessing risk for trisomy 21 by measurement of fetal NT thickness at 11 to 13 weeks' gestation. They analyzed samples by full karyotyping and by qf-PCR for chromosomes 13, 18, 21, X, and Y.

They found the fetal karyotype to be normal in approximately 89% of cases and abnormal in the remaining 11%. The researchers calculated that while relying entirely on karyotyping reveals all clinically significant chromosomal abnormalities and relying entirely on qf-PCR identifies 97.9%, the combination strategy identifies 99% of significant abnormalities at 60% of the cost of full karyotyping for all.