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A new test may be better at detecting potentially harmful genetic change in children before they are tolerate than current methods , researchers say .
The test , call a chromosomal microarray , observe more irregularity that could result ingenetic diseases — such as missing or reiterate sections of genetic code — than did karyotyping , which is the current standard method of antepartum examination .
A DNA molecule.
For instance , child who are miss a little serving of chromosome 22 will be born with DiGeorge syndrome , which can do severe heart fault and developmental delay . In the subject field , a chromosomal microarray find this neglect surgical incision and diagnose the condition , whereas a karyotype is not capable to find the change .
Microarrays also identified some genetic changes link up toautismnot bring out by karyotyping .
The findings suggest microarray should put back karyotyping as the standard method of finding genetic constipation in fetuses , said study research worker Dr. Ronald Wapner , an accoucheur and woman’s doctor at Columbia University in New York . Microarrays are already used todiagnose genetic conditions in childrenwith developmental disabilities and nascency defect .
However , experts admonish that microarrays could leave more information than is useful . Some abnormalities name by the psychometric test are new , and have unnamed or uncertain aftermath , which can put tension on home . [ See11 Big Fat Pregnancy Myths . ]
It is critical that parent who pick up this case of testing are counseled before and after the test about what the findings could stand for , experts say .
Microarrays vs. karyotype
In karyotyping , fetal cells are canvass under a microscope , which allows researchers to see whether too many or too few chromosomes are present , or if the chromosomes have an abnormal structure . In contrast , microarrays compare a sample of the foetus ' DNA with that of a healthy someone , giving researcher a closer look at the hereditary code .
Both tests necessitate fetal cells , which are obtained either by amniocentesis , a procedure that takes cells from the amnionic fluid , or chorionic villus sampling , which takes cadre from the placenta . These procedures comes with risks , include a little risk ofmiscarriage .
In the subject area , Wapner and colleagues analyze information from about 4,400 fraught women who had antenatal testing because they were over 35 , had an abnormal result on screeningtest for Down syndrome , or they had an echography that indicated possible nascence defects .
Microarray testing was just as good as karyotyping at detect whether the fetus had too many or too few total chromosome .
In gain , about 2.5 per centum of sample with a normal karyotype had microarray event that revealed neglect or repeated sections of inherited code that could result in a genic disease .
For fetuses with potential birth defect , about 6 percentage of samples with a normal karyotype had abnormalities on the microarray .
In a second study , also published today , microarrays more often provided results on genetic examination looking for the cause of a stillbirth — 87 percent microarray tests produced results equate with 70 pct with karyotype .
When to habituate microarrays
Dr. Manny Alvarez , an obstetrician and medical editor for FoxNews , enounce he agreed with the conclusion that microarrays should supercede karyotyping . " I will sure as shooting be adding microarrays " when conducting amnio tests , Alvarez sound out .
Also , karyotyping requires bouncy cubicle , and if cells fail to grow in a science lab , the amniocentesis must be repeated , Alvarez said . Microarrays do n’t require unrecorded cellphone , and so they do not have this trouble , he enounce .
Some doctor have held back on using microarrays for antenatal examination because it ’s not always clear how a hereditary disease will evidence , tell Dr. Monique Ho , an obstetrician and prenatal geneticist at the University of Rochester Medical Center , who was not involved in the field of study . One shaver with a picky genic variation may be disabled , while another with the same chromosomal mutation may appear healthy .
But as databases of genetic abnormalities produce , and research worker study nestling for longer periods , understanding of what genetic finding mean will improve , Wapner said .
Ho said microarrays could exchange karyotyping in some but not all cases . doctor might need to use microarrays if time is a factor , because the trial is faster than karyotyping .
However , microarrays can not dependably detect a phenomenon know as mosaicism , in which a genetic mental defectiveness is detect in some cells , but not all of them , Ho enunciate . Microarrays also can not observe change in which there is no loss or increase of DNA , which could bear upon the next coevals of children , Ho said .
The new studies will be published tomorrow ( Dec. 6 ) in the New England Journal of Medicine .
Pass it on : The stock method acting for antepartum testing , calledkaryotyping , may be mostly supersede by a young trial called a chromosomal microarray .
