Researchers find fast, cheap way to test for birth defects

NEW YORK • After 10 years of effort, medical researchers at Columbia University have developed a very fast and cheap way to detect the extra or missing chromosomes that most often cause miscarriages or severe birth defects.

The method, described on Wednesday in the New England Journal of Medicine, takes less than two hours using a palm-size device and costs US$200 (S$280) per use. With current testing procedures, women can end up paying US$1,000 to US$2,000, often out of pocket.

The technique, developed by Dr Zev Williams, director of the Columbia University Fertility Centre, and his colleagues, uses cells and tissues obtained from existing pre-natal screening procedures of embryos and foetuses, or tissue obtained after miscarriages.

Its key advantage is that the cells or tissue do not have to be sent to a testing lab - the analysis can be done in the same office that obtained the material, and results are ready in hours rather than days or weeks.

Dr Williams' results still need to be confirmed by outside studies. But the method could help women better understand what caused their miscarriages. For those who have embryos tested during in-vitro fertilisation, it would also avoid lengthy waits for results. The same would be true of women who have pre-natal testing of foetuses with amniocentesis or chorionic villus sampling, known as CVS.

And for women in states that have restricted abortion to within the first 15 or 18 weeks of a pregnancy, it could provide a bit more lead time in deciding whether to terminate a pregnancy.

Current screening methods, sent to centralised labs, involve lengthy wait times.

The longest delay in getting test results is for those who have had miscarriages. They may have to wait several weeks because labs must first grow cells in order to have thousands to examine, said Dr James Grifo, programme director of the New York University Langone Fertility Centre, who was not involved in the new study.

Dr Mark Hornstein, director of the division of reproductive endocrinology and infertility at Brigham and Women's Hospital in Boston, said the cultured cells sometimes died before they could be tested. "It is very difficult to keep cells alive and not contaminated for three weeks," he added.

"Not infrequently, we get no growth. We wait three weeks and the lab tells us, 'You have no cells.'"

The new test avoids these delays by using a method called nanopore sequencing, which was developed to read the sequences of very long strands of DNA but has not been used to look for chromosomal anomalies.

Dr Williams and his colleagues modified the preparation of DNA samples to use nanopore sequencing with small DNA pieces.

Each DNA segment should appear as two copies - one from each chromosome. If there are three copies, that means there is an extra chromosome; if there is one copy, that means a chromosome is missing.

Chromosome testing can provide important information for women and their doctors because extra or missing chromosomes are usually fatal to embryos.

Foetuses that survive with them often have severe birth defects.

The best-known example - Down syndrome - is "actually one of the mildest", Dr Williams said.

That can be important for in-vitro fertilisation. The older a woman is, the more likely that an embryo will have chromosomal abnormalities.

For 30-year-old women, the risk is 25 per cent. It is 75 per cent in women at age 42.

Dr Hornstein, who was also not associated with the study, cautioned that the test was not yet ready for widespread use.

There has to be independent studies that confirm that its results are accurate, and there must be evidence that it is "technically easy enough that any lab can do it", he said. But he added that if those conditions are met, he expects the test to be adopted widely.

NYTIMES