OHSU Now Offers Screening for Carriers of Cystic Fibrosis

06/16/04    Portland, Ore.

 

Oregon Health & Science University, the state's only provider of clinical molecular genetic testing, now offers carrier screening tests for cystic fibrosis, an incurable and frequently fatal disease of the mucus glands.


The purpose of CF carrier testing is to determine whether a couple is at increased risk for giving birth to a child who will have CF. Carrier testing is a laboratory test performed on a sample of blood or mouthwash, and testing must be ordered through a physician and only after the process of patient education and with the patient's consent.

In 1998, based on two National Institutes of Health Consensus Development Conferences, the American College of Obstetricians and Gynecologists and the American College of Medical Genetics issued formal guidelines recommending that CF carrier testing be available to couples planning a pregnancy or who are pregnant.

"OHSU DNA Diagnostic Laboratory is pleased to offer cystic fibrosis carrier screening testing, which complies with the guidelines of the American College of Obstetrics and Gynecology and the American College of Medical Genetics," said Carolyn Sue Richards, Ph.D., professor of molecular and medical genetics, and the laboratory's director.

"We believe that responsible implementation of the CF carrier test, along with genetic counseling, is crucial to couples' ability to make more informed decisions as they look toward planning families. Today, genetic testing for CF provides parents and physicians with the tools to plan ahead. We are committed to bringing this service to the Oregon health care community."

Robb Moses, M.D., professor and chairman, Department of Molecular and Medical Genetics, OHSU School of Medicine, credited Richards for bringing the test to Oregon.

"OHSU is very fortunate to have Dr. Richards join our team because she's nationally recognized as a leader in implementing this test for the benefit of patients," he said.

The test's availability in Oregon means the results will be more readily available and less expensive to couples planning a pregnancy, said Jone Sampson, M.D., OHSU assistant professor of molecular and medical genetics, and obstetrics and gynecology.

"More importantly, we have a number of genetic counselors and geneticists who are available to provide consultation regarding the screening test results and the risks for having an affected fetus," she said.

According to the Cystic Fibrosis Foundation, CF is a genetic disease affecting about 30,000 children and adults in the United States with more than 1,000 new cases each year. A genetic mutation, or a defective gene, causes the body to produce an abnormally thick, sticky mucus that clogs the lungs and leads to life-threatening lung infections. These secretions also obstruct the pancreas, preventing digestive enzymes from reaching the intestines to help break down and absorb food.

An individual must inherit two defective CF genes -- one from each parent -- to have CF. If both parents carry the mutation, there is a 25 percent chance that their child will have CF; a 50 percent chance that the child will be a carrier of the CF gene; and a 25 percent chance the child will be a noncarrier.

More than 10 million Americans -- one in every 31 -- are asymptomatic carriers of the defective gene, according to the American College of Obstetricians and Gynecologists. The disease is more common among Caucasian and Ashkenazi Jewish populations compared with African Americans and Hispanic Americans, and it is much less common among Asian Americans.

Understanding variations in the genetic code is vital to the development of new medical diagnostic and therapeutic products. While individual traits, such as hair and eye color, are determined by normal genetic variations, abnormal variations or mutations can create disease states, such as cystic fibrosis, deafness or cancer. Genetic tests, such as the CF test, look for abnormalities in a person's genes. In the case of CF, one mutation in a healthy individual indicates that this individual is a carrier of the disease gene, while two mutations in a symptomatic individual confirms the diagnosis of CF.

The CF screening test is a DNA test that involves using PCR, or polymerase chain reaction, to identify mutations in the CF gene. This process involves the amplification, or copying, of specific regions of the gene to produce enough DNA for mutation analysis. While there are more than 1,000 mutations in the CF gene, the CF assay used by the OHSU DNA Diagnostic Laboratory screens for the 32 most common mutations, including 25 of the mutations recommended by ACOG and ACMG, which will identify approximately 90 percent of CF carriers in the Caucasian population.

The test's carrier detection rate is less in African Americans and Hispanic Americans, and significantly less in Asian Americans.

The OHSU DNA Diagnostic Laboratory has provided Oregon health care with state-of-the-art, DNA-based testing for diagnosis, carrier detection and prenatal diagnosis for various genetic diseases for more than 10 years. Additional categories of its genetic tests include those for various muscular dystrophies, mental health syndromes and neurological disorders, as well as for other genetic diseases. The directors are faculty members in the departments of Molecular and Medical Genetics and Pathology and are boarded in clinical molecular genetics by the American Board of Medical Genetics.

The laboratory is certified by the Clinical Laboratory Improvement Act and the College of American Pathologists. Test development at the laboratory is ongoing and is tightly linked with the needs of the Oregon community and new research developments at OHSU.

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