Traditionally, when considering genetic reproductive risks, individuals have been offered carrier screening for conditions more commonly seen within their ethnic background. For example, those of Ashkenazi Jewish descent were offered screening for diseases such as Tay-Sachs and Canavan, while those of African or Mediterranean descent were offered screening for blood disorders, such as sickle cell disease or thalassemia.
The ethnic admixture of the US population, however, is becoming increasingly more diverse. Couples often present to the clinic without knowledge of their ethnic background or with multiple ethnic backgrounds, which may make selecting an appropriate carrier screening panel challenging.
To meet the rising demand for comprehensive carrier screening, Emory Genetics Laboratory (EGL) developed the Pan-Ethnic Carrier Screen, which costs patients and the healthcare industry significantly less than individual disorder testing by including analysis for many genetic conditions on one sample.
“The Pan-Ethnic Carrier Screen employs next generation sequencing technology and analyzes more genes, spanning more genetic disorders, than any other carrier screen currently available,” says Madhuri Hegde, PhD, FACMG, professor of human genetics at Emory University School of Medicine and executive director of Emory Genetics Laboratory.
In total, the test screens for 725 mutations across 145 genes, related to more than 140 genetic disorders, which includes all mutations recommended for screening by the American College of Medical Genetics and Genomics and the American Congress of Obstetricians and Gynecologists.
“A lot of care and expertise went into compiling the mutation list,” Hegde says. “We specifically wanted to avoid milder adult-onset diseases, autosomal dominant conditions, or mutations that are cosmetic or not clinically relevant. Additionally, we were able to pull from our expertise in the area of metabolic and lysosomal storage disorder diagnostics to add common mutations seen in these disorders to the panel.”
The Pan-Ethnic Carrier Screen tests for mutations associated with cystic fibrosis, diseases common in the Ashkenazi Jewish population, red blood cell disorders, metabolic disorders, lysosomal storage disorders, and X-linked conditions, including fragile X syndrome. Multiple testing options are available, including optional carrier screening for spinal muscular atrophy.
Ideally, carrier screening is performed pre-conception, but it can also be offered to assess risks during pregnancy. Although a positive test result should not affect the mother’s health, there could be up to a 25 percent chance for her baby to be affected, depending on the carrier status of the partner.
For the patient, detailed information is available on pre- and post-test risks, along with potential reproductive risks given different partner result scenarios. Counseling support is available for clinicians if needed.
In addition to the targeted mutation panel, EGL offers a variety of follow-up testing options such as full gene sequencing for partners of identified carriers, testing for specific mutations identified on the panel for family members of identified carriers, and prenatal diagnosis when both partners are identified as carriers.
Custom targeted mutation analysis can also be ordered for patients with a known familial mutation not on EGL's panel and who also wish to have the Pan-Ethnic Carrier Screen for the remaining conditions. This makes it easier for healthcare providers to know where to turn when the need for additional testing arises for families. It also helps ensure accurate identification of rarer mutations in family members and eliminates the need for duplicate confirmations, Hegde says.
“The Pan-Ethnic and Ashkenazi Jewish Carrier Screens offer patients and clinicians the most comprehensive molecular analysis available for assessing reproductive risk. The fact that all follow-up testing can also be performed at EGL is added value,” says Stephen Warren, PhD, FACMG, chairman of the Department of Human Genetics, Emory University School of Medicine, and founder of Emory Genetics Laboratory. “EGL offers fully integrated biochemical, molecular, and cytogenetic testing, and the addition of these new carrier screens further rounds out EGL offerings. Many commercial laboratories, and even other academic laboratories, focus on only certain disorders and don’t bring to the table the level of expertise in genetic diagnostics that EGL offers.”