Joint SOGC-CCMG Opinion for Reproductive Genetic Carrier Screening: An Update for All Canadian Providers of Maternity and Reproductive Healthcare in the Era of Direct-to-Consumer Testing

ObjectiveThis guideline was written to update Canadian maternity care and reproductive healthcare providers on pre- and postconceptional reproductive carrier screening for women or couples who may be at risk of being carriers for autosomal recessive (AR), autosomal dominant (AD), or X-linked (XL) conditions, with risk of transmission to the fetus. Four previous SOGC- Canadian College of Medical Geneticists (CCMG) guidelines are updated and merged into the current document.Intended UsersAll maternity care (most responsible health provider [MRHP]) and paediatric providers; maternity nursing; nurse practitioner; provincial maternity care administrator; medical student; and postgraduate resident year 1-7.Target PopulationFertile, sexually active females and their fertile, sexually active male partners who are either planning a pregnancy or are pregnant (preferably in the first trimester of pregnancy, but any gestational age is acceptable).OptionsWomen and their partners will be able to obtain appropriate genetic carrier screening information and possible diagnosis of AR, AD, or XL disorders (preferably pre-conception), thereby allowing an informed choice regarding genetic carrier screening and reproductive options (e.g., prenatal diagnosis, preimplantation genetic diagnosis, egg or sperm donation, or adoption).OutcomesInformed reproductive decisions related to genetic carrier screening and reproductive outcomes based on family history, ethnic background, past obstetrical history, known carrier status, or genetic diagnosis.SOGC Reproductive Carrier Screening Summary Statement (2016)Pre-conception or prenatal education and counselling for reproductive carrier screening requires a discussion about testing within the three perinatal genetic carrier screening/diagnosis time periods, which include pre-conception, prenatal, and neonatal for conditions currently being screened for and diagnosed. This new information should be added to the standard reproductive carrier screening protocols that are already being utilized by the most responsible maternity provider through the informed consent process with the patient. (III-A; GRADE low/moderate)SOGC Overview of Recommendations Quality and GradeThere was a strong observational/expert opinion (quality and grade) for the genetic carrier literature with randomized controlled trial evidence being available only for the invasive testing. Both the Canadian Task Force on Preventive Health Care quality and classification and the GRADE evidence quality and grade are provided.EvidenceMEDLINE; PubMed; government neonatal screening websites; key words/common reproductive genetic carrier screened diseases/previous SOGC Guidelines/medical academic societies (Society of Maternal-Fetal Medicine [SMFM]; American College of Medical Genetics and Genomics; American College of Obstetricians and Gynecologists [ACOG]; CCMG; Royal College Obstetrics and Gynaecology [RCOG] [UK]; American Society of Human Genetics [ASHG]; International Society of Prenatal Diagnosis [ISPD])/provincial neonatal screening policies and programs; search terms (carrier screening, prenatal screening, neonatal genetic/metabolic screening, cystic fibrosis (CF), thalassemia, hemoglobinopathy, hemophilia, Fragile X syndrome (FXS), spinal muscular atrophy, Ashkenazi Jewish carrier screening, genetic carrier screening protocols, AR, AD, XL).Search Period10 years (June 2005-September 2015); initial search dates June 30, 2015 and September 15, 2015; completed final search January 4, 2016.Validation of articles was completed by primary authors RD Wilson and I De Bie.Benefits, Harms, and CostBenefits are to provide an evidenced based reproductive genetic carrier screening update consensus based on international opinions and publications for the use of Canadian women, who are planning a pregnancy or who are pregnant and have been identified to be at risk (personal or male partner family or reproductive history) for the transmission of a clinically significant genetic condition to their offspring with associated morbidity and/or mortality. Harm may arise from having counselling and informed testing of the carrier status of the mother, their partner, or their fetus, as well as from declining to have this counselling and informed testing or from not having the opportunity for counselling and informed testing. Costs will ensue both from the provision of opportunities for counselling and testing, as well as when no such opportunities are offered or are declined and the birth of a child with a significant inherited condition and resulting morbidity/mortality occurs; these comprise not only the health care costs to the system but also the social/financial/psychological/emotional costs to the family.These recommendations are based on expert opinion and have not been subjected to a health economics assessment and local or provincial implementation will be required.Guideline UpdateThis guideline is an update of four previous joint SOGC-CCMG Genetic Screening Guidelines dated 2002, 2006, 2008, and 2008 developed by the SOGC Genetic Committee in collaboration with the CCMG Prenatal Diagnosis Committee (now Clinical Practice Committee).2016 Carrier Screening RecommendationsPrimary principles for carrier screening1.A primary discussion about the value and risk of reproductive carrier screening should be offered to all women/families considering a pregnancy (pre-conception) and to all pregnant women at their first prenatal visit, regardless of gestational age at the time of presentation. (III-A) (GRADE low/moderate)2.Women should be asked, preferably in the pre-conception period, about a family history or personal manifestations of intellectual disability, muscular dystrophy, or bleeding disorders. Particular attention should be paid to X-linked conditions such as Fragile X syndrome, Duchenne/Becker muscular dystrophy (1/4000 male births), hemophilia A (1/5000 male births), and hemophilia B (1/30,000 male births). (III-A) (GRADE low/moderate)3.A positive history of potential genetic/syndromic and chromosomal disorders as well as congenital anomalies, intellectual disability, stillbirth, sudden death, and other major health concerns such as cardiomyopathy, epilepsy, hearing loss, autism, and psychiatric disorders obtained as part of a three-generation pedigree review requires timely consultation referral to a reproductive genetic provider. (III-A) (GRADE low/moderate)4.Genetic counselling should be offered to women/families identified as being at risk of transmission of an inherited condition based on a three-generation pedigree review, ethnic background, or past medical/obstetrical history. Information on ethnic origin and province/country of recent family residence may be helpful in choosing appropriate screening studies. Direct gene mutation or expanded next generation gene sequencing testing should be discussed as part of the informed consent process. (II-2A) (GRADE moderate/moderate)5.When both reproductive partners are identified as carriers of the same autosomal recessive condition, the couple should be promptly referred for formal genetic counselling, preferably before conception or as early in the pregnancy as possible due to the complexity of the counselling/informed consent process and the 25% transmission risk to their offspring. (II-3A) (GRADE moderate/moderate)Fragile X syndrome and related disorders1.Fragile X syndrome is an X-linked condition with significant clinical implications for the carrier and her relatives. Any woman with a personal or family history of Fragile X- or Fragile X mental retardation 1-related disorders; unexplained intellectual disability or developmental delay; autism; ovarian insufficiency with elevated follicle stimulating hormone at age < 40 years of unknown etiology; or any woman with a family history of male relatives with developmental delay, autism, or isolated cerebellar ataxia and tremor should be offered screening for this condition. (II-2A) (GRADE moderate/moderate)2.History alone is appropriate for consultation by a medical genetics specialist, as family confirmation can be difficult to obtain and may delay carrier testing, especially if pregnant. (II-2A) (GRADE moderate/moderate)3.Fragile X carrier testing must only occur after detailed genetic counselling and informed consent from the woman to be tested has been obtained. (III-A) (GRADE low/moderate)4.Population carrier screening for Fragile X syndrome in all women of reproductive age cannot be recommended at this time. (II-2D) (GRADE moderate/moderate)X-linked hemophilia1.A maternal family history of bleeding disorders in a woman's male relatives (father, brother and/or maternal uncles) requires genetic counselling and the offer of carrier testing for the specific bleeding disorder in the family. If the diagnosis is unknown or cannot be confirmed, carrier testing for hemophilia A and B should be offered.Thalassemia/hemoglobinopathies1.Carrier screening for hemoglobinopathies should be offered to women/families from ethnic backgrounds with a reported increased carrier frequency, when red blood cell indices reveal a mean cellular volume < 80 fl, or electrophoresis reveals an abnormal hemoglobin type. However, the use of ethnicity alone in the carrier risk identification process may create screening inconsistency and missed opportunity for carrier identification, with both obstetrical and fetal implications. High clinical suspicion is required as well. Screening should be done in the pre-conception period or as early into the pregnancy as possible. (II-2A) (GRADE moderate/moderate)2.Carrier screening for thalassemia/hemoglobinopathies should be offered by the most responsible health care provider or reproductive genetic provider and include:
- Complete blood count
- Hemoglobin (Hb) electrophoresis (HE) or Hb high performance liquid chromatography (HHPLC)
- Quantification of Hb alpha 2 and fetal Hb
- Serum ferritin/H bodies (blood smear stain using brilliant cresyl blue) if microcytosis (mean cellular volume < 80 fl) and/or hypochromia (mean cellular Hb < 27 pg) in the presence of a normal HE or HHPLC assessment. (II-2A) (GRADE moderate/moderate)3.If the female thalassemia screening results are abnormal, a hemoglobinopathy screening protocol should be undertaken for the male partner. (III-A) (GRADE low/moderate)4.If both reproductive partners are found to be carriers of thalassemia or a combination of thalassemia and hemoglobin variant, they should be referred for formal genetic counselling (reproductive risks, recommended prenatal testing, and diagnostic management). (II-3A) (GRADE moderate/moderate)Cystic fibrosis1.Cystic fibrosis carrier screening pre-conception or in pregnancy should be offered to women/families who may be at an increased risk of an affected child due to ethnic background, personal or family history, or clinical manifestations of this condition in themselves or the pregnancy. Pre-conception carrier screening is preferable. (II-2A) (GRADE moderate/moderate)2.The routine screening of all pregnant women to determine their cystic fibrosis carrier status is not recommended at this time. (III-D) (GRADE low/moderate)3.French Canadians with family origins from the Quebec regions of Saguenay Lac-St-Jean and Charlevoix should be routinely offered cystic fibrosis carrier screening due to the increased carrier frequency of 1/15 and 1/20, respectively, in individuals originating from these regions. (II-2A) (GRADE high/high)Ashkenazi Jewish population1.The definition for an Ashkenazi Jewish (AJ) heritage is determined as having at least one grandparent of AJ background. (III-A) (GRADE moderate/moderate)2.For couples of Ashkenazi Jewish heritage, routine carrier screening for Tay-Sachs disease (carrier frequency 1/30); Canavan disease (carrier frequency 1/37-1/53); and familial dysautonomia (carrier frequency 1/32) should be offered, preferably pre-conception or as early in pregnancy as is possible. (II-2A) (GRADE moderate/high)3.When only one member of a couple is of Ashkenazi Jewish ancestry, screening for the couple should be offered for Tay-Sachs disease only using biochemical hexosaminidase enzyme activity. (II-2A) (GRADE moderate/moderate)4.When only one member of a couple is of Ashkenazi Jewish (AJ) ancestry, screening should not be offered for familial dysautonomia and Canavan disease because of low carrier frequency in individuals who are not of AJ heritage and concurrent limitations of carrier screening in this situation. (III-D) (GRADE moderate/moderate)5.Additional Ashkenazi Jewish carrier screening should be offered when a positive family is elicited for one of the conditions known to be present at an increased frequency in this population (associated carrier frequencies are listed): Bloom syndrome 1/104; Fanconi anemia group C 1/89; Niemann-Pick type A 1/90; mucolipidosis type IV 1/100-127; Gaucher disease 1/18; glycogen storage disease type 1a 1/64; familial hyperinsulinism 1/68; maple syrup urine disease 1/97; dihydrolipoamide hydrogenase deficiency 1/107; CF 1/28; Usher syndrome 1/120; nemaline myopathy 1/168; Joubert syndrome 1/92; Walker-Warburg syndrome 1/150. (III-A) (GRADE moderate/high)Founder effects1.Women/families whose families have originated from the Quebec Bas-St-Laurent (Rimouski) and Gaspesie regions as well as from adjoining New Brunswick territories, or whose family history is positive for this condition, should be offered Tay-Sachs carrier screening due to carrier frequency of 1/14 in this particular geographic aggregate. (II-2A) (GRADE high/high) As well, couples for whom each partner has at least one grandparent originating from Saguenay Lac-St-Jean/Charlevoix region should be offered screening for the four common conditions present at a higher carrier frequency in this population due to founder effects: Tyrosinemia type I (carrier frequency 1/19), congenital lactic acidosis from Saguenay Lac-St-Jean (Leigh syndrome French Canadian type, carrier frequency 1/23), spastic ataxia, Charlevoix-Saguenay type (carrier frequency 1/23), and agenesis of the corpus callosum with peripheral neuropathy (carrier frequency 1/23).2.Careful three-generation family review for couples originating from regions with founder effects is mandatory, as other clinically relevant conditions may present with a higher incidence in these populations (e.g., cerebro-oculo-facio-skeletal syndrome in aboriginal Manitoba populations; myotonic dystrophy type I, congenital disorder of glycosylation type 1B, Tay-Sachs disease, and mucolipidosis II in populations from Saguenay Lac-St-Jean; and neuronal ceroid-lipofuscinosis and Bardet Biedl in populations originating from Newfoundland). The maternity care provider should remain alert to these specific regional founder effects.3.Women/families of Cree ancestry should be asked about previous screening for Cree leukoencephalopathy and Cree encephalitis, two devastating congenital neurodegenerative disorders with a founder effect in this population, for whom screening programs have been developed in their regional communities. If the couple has not been screened or does not recall their screening results, screening for these conditions should be undertaken as early as possible, ideally in the pre-conception period.4.Women/families with a possible heritage from Amish, Mennonite, and Hutterite religious groups based on family history and/or geographic or religious settlement locality should have a three-generation pedigree with founder effect considerations and referral to provincial medical genetic services if increased or possible connection is identified.Spinal muscular atrophy1.Routine spinal muscular atrophy (SMA) reproductive carrier screening cannot be recommended at this time as laboratory infrastructures as well as clinical and counselling resources are not universally available across Canada. However, a family history of SMA should alert the provider to an increased carrier risk for one member of the couple. Prompt referral to a reproductive medical genetics provider is strongly recommended (education and counselling). (II-2D) (GRADE moderate/moderate)Diagnosis and follow up1.Directed diagnostic fetal or neonatal laboratory (genetic/metabolic) testing or directed diagnostic postmortem pathology/autopsy evaluation is recommended to allow for appropriate diagnostic and recurrence risk counselling. (III-A) (GRADE low/moderate)2.A timely postnatal follow up by the most appropriate or available primary care physician, geneticist, obstetrician, neonatologist, or maternal fetal medicine provider(s) should be offered for any couple with a pregnancy established to be affected with an inherited condition identified by either prenatal or neonatal testing. (III-A) (GRADE low/moderate)3.Parents should be advised and educated about the estimated genetic recurrence risk in a subsequent pregnancy. (III-A) (GRADE low/moderate)Direct-to-consumer or self-pay physician ordered carrier testing1.Women/families who choose to undergo testing though either direct-to-consumer genetic testing or self-pay physician ordered testing, and who are subsequently found to be carriers of an inherited condition, have to be made aware prior to testing that access to formal genetic counselling may be limited. As well, additional confirmatory testing may be required but access may be limited by local resources or availability of the test in accredited laboratories. Ideally, individuals or couples who have been identified to be “at risk” for the transmission of a clinically significant genetic condition to their offspring by their primary care giver should be referred in the pre-conception period to a reproductive medical genetic provider for education and discussion of the implications for the couple and their offspring. (III-A) (GRADE moderate/moderate)