Identifying Robertsonian Translocation Carriers by Microarray-Based DNA Analysis.

OBJECTIVE: To develop a noninvasive prenatal testing improvement that allows identification of Robertsonian translocation carriers.

METHODS: Blood samples from 191 subjects, including 7 pregnant and 9 non-pregnant Robertsonian translocation carriers, were analyzed for fetal trisomy and Robertsonian translocation status. Digital Analysis of Selected Regions (DANSR™) assays targeting sequences common to the p arms of 5 acrocentric chromosomes were developed and added to existing DANSR assays. DANSR products were hybridized onto a custom DNA microarray for DNA analysis. The Fetal-Fraction Optimized Risk of Trisomy Evaluation (FORTE™) algorithm measures the fraction of fetal DNA and accounts for both the fetal and maternal fractions in the cell-free DNA sample to determine Robertsonian risk. The expectation in a Robertsonian translocation carrier is that DANSR assays on acrocentric p arms should have a concentration 20% less than that of controls.

RESULTS: The FORTE algorithm correctly classified the fetal trisomy status and maternal Robertsonian translocation status in all 191 samples. Sixteen samples had a Robertsonian risk score above 99%, while 175 samples had a Robertsonian risk score below 0.01%.

CONCLUSIONS: Robertsonian translocations are the most common chromosomal translocations and can have significant reproductive consequences. A maternal screen for Robertsonian translocation carriers would provide women valuable information regarding the risk of fetal trisomy.