Early Testing for Down Syndrome

A study has shown that a combined blood test and an ultrasound exam can identify more than 90% of cases of Down syndrome in the first trimester of pregnancy. This early screening test is an alternative to the conventional triple screen test and has the advantage of being performed 6-8 weeks earlier while detecting more cases of Down syndrome. The study was published in the August issue of Obstetrics and Gynecology.

Pregnant patients underwent an ultrasound exam in which the amount of fluid accumulation behind the neck of the baby, called nuchal translucency, was measured. A blood test then measured two chemicals called free beta hCG and PAPP-A. The results of the ultrasound measurement and blood test were entered into a mathematical formula to determine the risk level of Down syndrome. This screening test identifies the approximately 5% of patients who are most at risk for Down syndrome. These patients are then offered chorionic villus sampling or amniocentesis to determine definitely if the patient is carrying a baby with Down syndrome. The study results showed that 91% of women carrying a baby with Down syndrome were in this increased-risk group.

The study was conducted by collaborating researchers at Centro Di Diagnosi Prenatale (Palermo, Italy), NTD Laboratories (Huntington Station, NY, USA), GeneCare Medical Genetic Center (Chapel Hill, NC, USA), and The George Washington University Medical Center (Washington, DC, USA).

The test is marketed as UltraScreen by GeneCare Medical Genetics Center and NTD Laboratories. As advantages, they cite the 30% increased detection of Down syndrome, earlier reassurance to pregnant women who have normal results, and more time and diagnostic options for patients with increased risk results.