Genetic testing is an important part of diagnosing and treating chromosomal abnormalities. Currently, karyotyping is the most prevalent form of prenatal genetic testing, but the results of microarray testing appear to be more accurate, according to a study published in the New England Journal of Medicine. Researchers at Columbia University found microarray testing found all the same genetic abnormalities karyotyping found, but in some cases, microarray found hiccups in negative karyotyping results.
Researchers gathered information for the study over a five-year period. Genetic testing was completed on 4,400 women of advanced maternal age. As women age, the risk of genetic or chromosomal abnormalities increases, thus the older study population. In some cases, growth abnormalities were found via ultrasound with genetic testing completed after the finding to predict possible cause prior to birth, but not all cases presented with physical anomalies.
When growth issues were the cause of genetic testing, microarray found issues in 6-percent of women with no definitive results after karyotyping. Microarray also managed to find issues in 1.7-percent of pregnant women who passed the karyotyping test with no issues at all.
Microarray testing may also have a place in stillbirth testing. Karyotyping is known to provide inaccurate and unsuccessful results in up to 60-percent of stillbirth tests. Microarray, on the other hand, was able to provide a possible cause of stillbirth in 87-percent of the 532 cases tested. While knowing the cause of stillbirth after the fact will not stop the stillbirth it could help physicians establish a health care plan for the patient in future pregnancies to reduce the risk of stillbirth, if possible.
A microarray is a sensitive test. When the study was first started, about 2.5% of the abnormal test results were unexplained simply because doctors did not know how the chromosomal abnormality manifested in the fetus. By the end of the study that percentage dropped to 1.5%.
Source: Ronald J. Wapner, M.D., Christa Lese Martin, Ph.D., Brynn Levy, M.Sc.(Med.), Ph.D., Blake C. Ballif, Ph.D., Christine M. Eng, M.D., Julia M. Zachary, Melissa Savage, M.S et.al. Chromosomal Microarray versus Karyotyping for Prenatal Diagnosis. The New England Journal of Medicine, December 2012, DOI: 10.1056/NEJMoa1203382
http://www.nejm.org/doi/full/10.1056/NEJMoa1203382
