DNA fetus
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A same-day test to identify abnormal fetal chromosomes has been developed by a team of scientists. The Short-read Transpore Rapid Karyotyping (STORK) test detects extra or missing chromosomes using samples from miscarriages or prenatal tests, such as amniocentesis and chorionic villus sampling, as well as biopsies from pre-implantation embryos for in vitro fertilization (IVF).

Their findings were published in the New England Journal of Medicine this week. The study was led by Brynn Levy, PhD, and Zev Williams, MD, PhD, from Columbia University Fertility Center and Columbia University Irving Medical Center.

Current tests for aneuploidy include rapid and targeted techniques, such as fluorescence in situ hybridization, multiplex ligation-dependent probe amplification, and quantitative polymerase-chain-reaction assays. But these look at only a limited subset of chromosomes. Whole genome tests, such as G-banded karyotyping, chromosomal microarray analysis, and next-generation sequencing, are comprehensive. However, these typically take days to weeks, require testing at high-complexity centralized laboratories, and are costly to perform.

The STORK team writes that they: “Developed and validated a new short-read–based approach for library preparation, sequencing, and data analysis that enables accurate, inexpensive, and same-day genomewide aneuploidy detection with the use of a palm-sized, nanopore-based DNA sequencer.”

They compared STORK to standard methods by testing 218 samples that included tissue from miscarriage, chorionic villi, amniotic fluid and trophectoderm biopsies, which are used to evaluate embryos before IVF implantation. In this set of samples, STORK had an accuracy of 98 to 100%.

In another set of 60 samples, technicians in a clinical laboratory certified for quality testing performed STORK. In these samples, STORK was 100% in accordance with standard clinical testing.

Overall, STORK is comparable to standard clinical tests and has many advantages. It is faster, providing results within hours versus several days to weeks. It is also cheaper, with the study team estimating STORK to cost less than $50 per sample if 10 samples are run at the same time, or up to $200 if a sample is run on its own. STORK can also be done at the point-of-care for a patient, eliminating the need to ship a sample to a clinical laboratory.

Non-invasive prenatal tests have revolutionized genetic testing during pregnancy, but there are circumstances where a test such as STORK, because of its speed or lower cost, would be especially useful.

According to the study authors, STORK may, for example, be particularly useful in identifying genetic causes of miscarriage. Currently, professional societies only recommend genetic testing if a person has had multiple miscarriages, but an easy, cost-effective test like STORK could potentially be offered after the first miscarriage.

STORK could also be used to streamline the IVF process. Currently, embryos must be frozen while genetic tests are run and analyzed before implantation. STORK’s ability to provide results within hours can presumably eliminate this freezing step, which saves time and cost.

In addition, a speedier test could be useful for women in U.S. states with new restrictive abortion laws, so they can find out sooner about the genetic health of their fetus.

The researchers caution that more work is needed to validate STORK, but if results continue to show promise, the test could improve the quality of reproductive healthcare.

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