NIPS testing involves analyzing blood samples from pregnant women for DNA fragments derived from the placenta. These samples can reveal genetic or chromosomal conditions in a fetus, including Down syndrome, trisomies involving chromosomes 13 or 18, and extra or missing copies of the X or Y sex chromosomes.
The ACMG in 2016 published a set of recommendations for how NIPS testing should be conducted, including statistical parameters that should be part of each NIPS report:
- Detection rate: the percentage of fetuses with a condition that the test will accurately diagnose
- Specificity: the percentage of fetuses without a condition that will receive a negative result
- Positive predictive value (PPV): the percentage of fetuses with positive test results that actually have the condition
- Negative predictive value (NPV): the percentage of fetuses for which a negative test result will be accurate
- Fetal fraction: the percentage of cell-free DNA in the mother's bloodstream that originated from the placenta
Despite the guidance, the researchers found that none of the labs polled met all of the ACMG recommendations, although all labs met at least some of the recommendations. This lack of full reporting could have an impact on patients by leading to confusion and improper patient counseling, according to the group.
"The ACMG was clear that laboratories should not offer screening when some of their recommendations were not met, so I think our findings will be concerning to clinicians and expectant parents trying to identify quality NIPS reporting in today's marketplace," said Dr. Brian Skotko, from the division of medical genetics at MassGeneral Hospital for Children, in a statement. Skotko was the corresponding author on the paper.
The researchers hope the results will prompt commercial labs to revise their reports to include patient resources and test metric data that can help providers assist patients in making informed decisions, Skotko said. He and members of the Prenatal Research Information Consortium are maintaining a chart that shows the compliance of individual laboratories with the ACMG recommendations.
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