The Human Genome Project, completed on April 14, 2003, With collaboration from genetics specialists, genetic risk assessment, screening and testing can become an important part of primary medical care
Consultation with genetics specialiists is critical as the field is advancing at a rapid pace and genetic tests and interpretation of results are complex.
Purpose: To detect couples at risk of having children with prenatally diagnosable genetic diseases Guides to screening are in Genetics Resource Packet March of Dimes Genetic Screening Pocket Facts Preconception/prenatal family history assessment guide Insurance coverage for ethnicity-based carrier screening tests: Some insurers and some plans will cover testing, others will not. Each patient needs to check their personal plan prior to screening.
Appropriate carrier tests should be offered to each patient based on his/her ethnic background & family history Counseling before screening should include: Purpose of screening, voluntary nature of testing Range of symptoms and severity of each disease being screened for Risk of carrier status and affected offspring based on ethnicity Meaning of positive and negative results Factors to consider in deciding to have or not have testing
ACOG guidelines, Oct. 2001 recommend pffeing CF screening to: Persons with a family history of CF Reproductive partners of carriers or persons with CF Couples in whom one or both partners are Caucasian and are planning a pregnancy or seeking prenatal care AND “ Making CF screening available” to couples in other racial or ethnic groups at lower risk
Cannot emphasize enough that different mutations confer different risks! Know the details about a given mutation before talking to a patient. Consult with genetics or call the testing laboratory to get the most up-to-date information. Genetic counseling is available prior to testing should a couple want to discuss each of these disorders in more depth before making decisions about testing.
Standard of care to offer to persons of AJ background or their partners prior to conception or during 1 st trimester: Tay-Sachs disease Cystic Fibrosis Canavan disease
Make sure that if the patient is already pregnant, that screening is performed by leukocyte or platelet assay. This necessitates special drawing and handling which should be set up in advance. Make sure you send to a lab that offers this type of testing. Otherwise, look for such a lab on genetests.org
Detection rate much lower in non-AJ persons. Incidence of the disease in non-AJ population is very low as is carrier rate. Find testing labs through genetests.org
See GENETIC CARRIER SCREENING : OPTIONS FOR PERSONS OF ASHKENAZI JEWISH ANCESTRY in the resource packet. This fact sheet can be given to patients of AJ background Some genetics labs offer “AJ carrier panels” with various tests on them. Labs will also often have patient education materials. Be aware that different labs test for different mutations or panels of mutations and will have different detection rates.
See Sample Family History Questionnaire in resource packet Use for patients considering pregnancy or already pregnant Screens for patients who may have reproductive genetic risks. Not comprehensive – captures only genetic and maternal health information relevant to current/future offspring
Genetics and Primary Care Cystic Fibrosis and Ethnicity-Based Carrier Screening
Purpose: To detect couples at risk for prenatally diagnosable genetic diseases
Types of tests offered based on clients’ ethnic background
Offered to all individuals of that ethnic background (targeted population screening)
Population Condition Carrier Frequency Carrier Frequencies based on Ethnic Origin 1 in 25 1 in 29 1 in 40 Beta-Thalassemia Cystic Fibrosis Sickle Cell Mediterranean 1 in 46 1 in 30 - 1 in 50 Cystic Fibrosis Beta-Thalassemia Hispanic 1 in 30 Tay Sachs disease French Canadian, Cajun 1 in 25 - 1 in 29 Cystic Fibrosis European American 1 in 20 1 in 50 Alpha-Thalassemia Beta-Thalassemia Asian 1 in 15 1 in 26 - 1 in 29 1 in 30 1 in 32 1 in 40 Gaucher disease Cystic Fibrosis Tay-Sachs disease Dysautonomia Canavan disease Ashkenazi Jewish 1 in 10 1 in 65 1 in 75 Sickle Cell Cystic Fibrosis Beta-Thalassemia African-American
Genetic consultation is available to carriers and strongly advised for carrier/carrier couples
Carrier Rates: Cystic Fibrosis Not available ~30% (?) ~1/90 (?) Asian ~1 in 232 72% 1/65 African American ~1 in 105 57% 1/46 Hispanic ~1 in 97 to 1 in 140 70-80% 1/29 Southern European Caucasian ~1 in 930 97% 1/26 – 1/29 Ashkenazi Jewish ~1 in 250 85-90% 1/25 – 1/29 Northern European Caucasian Carrier risk after negative test Detection Rate Carrier Frequency Ethnic Group
Marcia is a 25 year old Caucasian woman who comes to her first prenatal visit at 9 weeks gestation. Her husband, Mark, age 28, also Caucasian, attends the visit with her. There is no family history of significance.
Her prenatal care provider, Ann Smith, NP, discusses the option of CF carrier screening with the couple.