CombiMatrix (CBMX) to Present Data from NIPT in Chromosomal Aneuploidies, Microdeletion Syndromes

October 9, 2015 6:46 AM EDT
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CombiMatrix (NASDAQ: CBMX) announces the presentation of data supporting the value of follow-up diagnostic testing to confirm or rule out positive results for common chromosomal aneuploidies and microdeletion syndromes detected by non-invasive prenatal testing (NIPT). Data from the unpublished study conducted by CombiMatrix were presented by Trilochan Sahoo, M.D., FACMG, CombiMatrix's Vice President of Clinical Affairs and Director of Cytogenetics, in a presentation late yesterday at the 2015 American Society of Human Genetics (ASHG) conference underway in Baltimore.

"The use of NIPT to detect common fetal chromosomal abnormalities is increasing, yet we found significant rates of false positive test results after subsequent follow-up testing with microarray and karyotyping," said Dr. Sahoo. "Importantly, in addition to the well-documented high false positive rates for some aneuploidies, our data show significant false positive rates for microdeletions. These data suggest NIPT results that are positive for an abnormality often turn out to be normal after a follow-up diagnostic test such as those offered by CombiMatrix. Our ability to expand upon the NIPT findings provides highly valuable diagnostic information to patients and their families."

Common chromosomal aneuploidies include Down (trisomy 21), Edwards (trisomy 18) and Patau (trisomy 13) syndromes. Chromosomal microdeletions are associated with conditions such as intellectual disability, seizures, autism spectrum disorder and neuropsychiatric disorder, among others.

The unpublished CombiMatrix study, "Expanding non-invasive prenatal testing to include microdeletions and segmental aneuploidy: Cause for concern?," was performed by Dr. Sahoo and evaluated outcome and concordance results of NIPT with invasive diagnostic testing using both fetal karyotype and/or prenatal microarray from 290 cases in women with both high- and low-risk pregnancies. Highlights of the study's findings include:

  • The overall true positive and false positive rates for NIPT compared to diagnostic testing were estimated at approximately 70% and 20%, respectively.
  • The chromosome-specific true positive and false positive rates, respectively, were 84% and 12% for Trisomy 21; 82% and 18% for trisomy 18; 53% and 47% for trisomy 13; and 44% and 56% for X-Y chromosome aneuploidies.
  • For 25 cases predicted by NIPT to have a microdeletion or duplication, the overall true positive and false positive rates were 30% and 70%, respectively. The outcomes for false positive rates were 71% for 22q11.2 deletion (DiGeorge syndrome); 75% for 1p36 deletion; and 83% for 5p deletion.

"Recently published findings suggest a cautious approach to the interpretation of NIPT results based on the higher-than-previously reported over-representation of the positive predictive value for specific aneuploidies," said Mark McDonough, President and Chief Executive Officer of CombiMatrix. "These new study data support that it is absolutely essential to follow-up positive results from NIPT with invasive prenatal diagnostic testing for both aneuploidies and microdeletions to preclude errors in diagnosis. The data suggest that a comprehensive approach in these situations benefits the patient and that clinical decisions should not be undertaken based purely upon NIPT results."

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