GRAPEVINE, TEX. — Chromosome microarray analysis may play a vital role in the diagnosis of genetic disorders prenatally, Christine Eng, M.D., commented during a meeting that was sponsored by the American College of Medical Genetics.
Although chromosome microarray analysis (CMA) already has an established role in the genetic evaluation of both children and adults, its use still is being evaluated in the prenatal setting.
“This study represents the initial use of CMA in pregnancies being monitored due to increased risk of chromosomal abnormalities,” said Dr. Eng of Baylor College of Medicine, Houston.
“It demonstrates a high level of acceptance and accuracy.”
Dr. Eng and her associates discovered that there was a 71% acceptance rate of CMA among couples in which the woman was undergoing amniocentesis or chorionic villi sampling (CVS).
Reasons for acceptance of the CMA test included having a previous child with anomalies, an abnormal ultrasound finding, maternal age, and a desire to learn as much as possible about the current pregnancy.
Reasons for declining testing included the perception that the disorders being tested were rare and concern that the test results would raise anxiety.
The study also demonstrated that the CMA test is highly accurate: Only 13% of the initial tests showed inconclusive results.
The study was undertaken to determine the reliability of CMA to detect cytogenetic abnormalities in fetal samples, design a program of parental counseling, and assess acceptance of CMA among couples who were undergoing prenatal diagnosis.
A total of 38 couples, who were recruited among patients undergoing amniocentesis or CVS, agreed to participate in the study.
Of the 38 samples assessed in the study, 60% were amniotic fluid and 37% were CVS. One was a fetal blood sample.
Indications for prenatal testing included advanced maternal age (58%), anomalies detected on fetal ultrasound (26%), and having a previously affected child (13%), Dr. Eng reported.
All genetic abnormalities that were detected by karyotype also were detected by CMA and consisted of three cases of trisomy 21, according to Dr. Eng.
In addition, in five of the cases (13%) initial CMA analysis yielded inconclusive results that required study of parental samples for further clarification.
The microarray that was used in the study contains 362 fluorescent in situ hybridization-verified clones that span genomic regions implicated in 55 known human genetic disorders as well as subtelomeric clones of all 41 relevant human chromosome telomeric regions.
“This greatly expands the capability to detect abnormalities in these regions, when compared with conventional prenatal karyotyping,” she said during the meeting.
Dr. Eng commented that additional experience will optimize patient education and counseling and yield further insight into the degree of normal variation in these regions.