Karen Chong

Technical Update: Preimplantation Genetic Diagnosis and Screening

OBJECTIVE To update and review the techniques and indications of preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS). OPTIONS Discussion about the genetic and technical aspects of preimplantation reproductive techniques, particularly those using new cytogenetic technologies and embryo-stage biopsy. OUTCOMES Clinical outcomes of reproductive techniques following the use of PGD and PGS are included. This update does not discuss in detail the adverse outcomes that have been recorded in association with assisted reproductive technologies. EVIDENCE Published literature was retrieved through searches of The Cochrane Library and Medline in April 2014 using appropriate controlled vocabulary (aneuploidy, blastocyst/physiology, genetic diseases, preimplantation diagnosis/methods, fertilization in vitro) and key words (e.g., preimplantation genetic diagnosis, preimplantation genetic screening, comprehensive chromosome screening, aCGH, SNP microarray, qPCR, and embryo selection). Results were restricted to systematic reviews, randomized controlled trials/controlled clinical trials, and observational studies published from 1990 to April 2014. There were no language restrictions. Searches were updated on a regular basis and incorporated in the update to January 2015. Additional publications were identified from the bibliographies of retrieved articles. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies. VALUES The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care. (Table 1) BENEFITS, HARMS, AND COSTS: This update will educate readers about new preimplantation genetic concepts, directions, and technologies. The major harms and costs identified are those of assisted reproductive technologies. SUMMARY Preimplantation genetic diagnosis is an alternative to prenatal diagnosis for the detection of genetic disorders in couples at risk of transmitting a genetic condition to their offspring. Preimplantation genetic screening is being proposed to improve the effectiveness of in vitro fertilization by screening for embryonic aneuploidy. Though FISH-based PGS showed adverse effects on IVF success, emerging evidence from new studies using comprehensive chromosome screening technology appears promising. Recommendations 1. Before preimplantation genetic diagnosis is performed, genetic counselling must be provided by a certified genetic counsellor to ensure that patients fully understand the risk of having an affected child, the impact of the disease on an affected child, and the benefits and limitations of all available options for preimplantation and prenatal diagnosis. (III-A) 2. Couples should be informed that preimplantation genetic diagnosis can reduce the risk of conceiving a child with a genetic abnormality carried by one or both parents if that abnormality can be identified with tests performed on a single cell or on multiple trophectoderm cells. (II-2B) 3. Invasive prenatal or postnatal testing to confirm the results of preimplantation genetic diagnosis is encouraged because the methods used for preimplantation genetic diagnosis have technical limitations that include the possibility of a false result. (II-2B) 4. Trophectoderm biopsy has no measurable impact on embryo development, as opposed to blastomere biopsy. Therefore, whenever possible, trophectoderm biopsy should be the method of choice in embryo biopsy and should be performed by experienced hands. (I-B) 5. Preimplantation genetic diagnosis of single-gene disorders should ideally be performed with multiplex polymerase chain reaction coupled with trophectoderm biopsy whenever available. (II-2B) 6. The use of comprehensive chromosome screening technology coupled with trophectoderm biopsy in preimplantation genetic diagnosis in couples carrying chromosomal translocations is recommended because it is associated with favourable clinical outcomes. (II-2B) 7. Before preimplantation genetic screening is performed, thorough education and counselling must be provided by a certified genetic counsellor to ensure that patients fully understand the limitations of the technique, the risk of error, and the ongoing debate on whether preimplantation genetic screening is necessary to improve live birth rates with in vitro fertilization. (III-A) 8. Preimplantation genetic screening using fluorescence in situ hybridization technology on day-3 embryo biopsy is associated with decreased live birth rates and therefore should not be performed with in vitro fertilization. (I-E) 9. Preimplantation genetic screening using comprehensive chromosome screening technology on blastocyst biopsy, increases implantation rates and improves embryo selection in IVF cycles in patients with a good prognosis. (I-B).

Referral patterns for microarray testing in prenatal diagnosis

Objective To understand the prenatal referral patterns from the United States, Canada, and Israel for two whole-genome microarray platforms, each with a different resolution. Method Physicians selected one of the two array designs to be performed on 1483 prenatal specimens for a 1-year period. We retrospectively examined detection rates, indications for study, and physician array selection. Results The lower resolution array (55 K) showed an ~32% decrease in the detection of results of unclear clinical significance while retaining the ability to detect all but one significant abnormality identified by the higher resolution array (135 K). A majority of samples were referred for abnormal ultrasound findings. Whereas the United States and Canada utilized the higher resolution array more often for this indication, Israel preferred the 55 K array. Referral patterns for parental anxiety were similar for the United States and Israel, with most cases being tested on the 55 K array. Few cases were referred for advanced maternal age or family history of a genetic condition from either Canada or Israel. Conclusion Referral patterns varied between the countries and between indications for study. Understanding these differences will provide laboratories the critical information needed to develop array designs to meet the medical needs and patient desires for prenatal testing.

Referral patterns for microarray testing in prenatal diagnosis: Microarray testing referral patterns

To understand the prenatal referral patterns from the United States, Canada, and Israel for two whole‐genome microarray platforms, each with a different resolution.

OEIS complex: prenatal ultrasound and autopsy findings

To describe prenatal ultrasound and autopsy findings in fetuses with OEIS (omphalocele, bladder exstrophy, imperforate anus, spina bifida) complex.

Diagnostic utility of microarray testing in pregnancy loss

To determine the frequency of clinically significant chromosomal abnormalities identified by chromosomal microarray in pregnancy losses at any gestational age and to compare microarray performance with that of traditional cytogenetic analysis when testing pregnancy losses.

Deletion of 15q11.2(BP1‐BP2) region: Further evidence for lack of phenotypic specificity in a pediatric population

Microdeletion of the BP1‐BP2 region at 15q11.2 is a recurrent copy number variant (CNV) frequently found in patients undergoing chromosomal microarray (CMA). Genetic counselling regarding this CNV is challenging due to the wide range of phenotypic presentation in reported patients and lack of general population‐based data. As one of the most common reasons for CMA is childhood developmental delay, clinicians need to be cognizant of the inherent ascertainment bias in the literature. We performed a detailed medical record review for 55 patients with this 15q11.2 microdeletion and report the clinical features of the 35 patients for whom information was available. We compared our results to the recent report by Cafferkey et al. in this journal. Our conclusion is that the phenotypic spectrum is too broad and non‐specific to constitute a bona fide “syndrome” and that further research must be done to delineate the contribution of this CNV to phenotype.

Raine syndrome: A rare lethal osteosclerotic bone dysplasia. Prenatal diagnosis, autopsy, and neuropathological findings†

Raine syndrome is an autosomal recessive condition with generalized osteosclerosis, characteristic facial dysmorphism and brain abnormalities including intracerebral calcifications. We report on a case with Raine syndrome born to nonconsanguineous couple and report the prenatal sonogram/MRI, the fetopathology, and neuropathology findings.

Fetal ventriculomegaly secondary to isolated large choroid plexus cysts: prenatal findings and postnatal outcome

To report the prenatal findings and postnatal outcome of fetal ventriculomegaly associated with isolated large choroid plexus cysts (CPCs).

Prenatal Diagnosis Procedures and Techniques to Obtain a Diagnostic Fetal Specimen or Tissue: Maternal and Fetal Risks and Benefits

OBJECTIVE To provide maternity care providers and their patients with current evidence-based guidelines for maternal risk/benefit counselling for a prenatally identified at-risk pregnancy that requires ultrasound-guided prenatal diagnostic procedures and/or techniques for a genetic diagnosis and for subsequent pregnancy management decisions on questions such as level of obstetrical care provider, antenatal surveillance, location of care and delivery, and continuation or termination of pregnancy. This guideline is limited to maternal risk/benefit counselling and pregnancy management decisions for women who require, or are considering, an invasive ultrasound-guided procedure or technique for prenatal diagnosis. PATIENT POPULATION Pregnant women identified as having an increased risk of a fetal genetic abnormality secondary to the process of established prenatal screening protocols (maternal serum±imaging, high-risk cell-free DNA results, abnormal diagnostic fetal imaging, or a positive family history of an inherited condition). These women may require or request counselling about pregnancy risks and benefits of an invasive ultrasound-guided procedure to determine the etiology, diagnosis, and/or pathology for the possible fetal anomaly or anomalies. EVIDENCE Published literature was retrieved through searches of Medline, PubMed, and the Cochrane Library in and prior to June 2014 using an appropriate controlled vocabulary (prenatal diagnosis, amniocentesis, chorionic villi sampling, cordocentesis) and key words (prenatal screening, prenatal genetic counselling, post-procedural pregnancy loss rate). Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies written in English and published from January 1985 to June 2014. Searches were updated on a regular basis and incorporated in the guideline to June 2014. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical speciality societies. VALUES The quality of evidence in this document was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1). Health benefits, side effects, and risks: Patient informed consent, knowledge translation, genetic prenatal risk assessment, anxiety relief, anxiety creation, advocacy, understanding or limitation for fetal testing, pregnancy management choice, pregnancy complication or loss, timely and improved care for birth of a neonate with recognized morbidity. Recommendations 1. The health care provider should counsel the at-risk pregnant woman on the different levels of genetic fetal testing in order for her to have a clear understanding and expectation of the level of testing and type of results that are offered. (III-B) 2. As part of the informed consent process, the health care provider should review with the at-risk pregnant woman the risks and benefits of in utero genetic diagnostic techniques associated with fetal genetic testing options. (III-A) 3. During risk/benefit counselling, the health care provider should advise that the best estimate of the pregnancy loss rate related to: a.amniocentesis is 0.5% to 1.0% (range 0.17 to 1.53%) (I) b.chorionic villus sampling is 0.5% to 1.0% (I) and c.cordocentesis or percutaneous umbilical blood sampling is 1.3% for fetuses with no anomalies and 1.3% to 25% for fetuses with single or multiple anomalies or intrauterine growth restriction. (II-2A).

Cornelia de Lange syndrome (CdLS): prenatal and autopsy findings.

Cornelia de Lange Syndrome (CdLS) is a multisystem disorder characterized by somatic defects and mental retardation. Prenatal diagnosis of this severe condition is difficult in view of the non‐specific ultrasound abnormalities. We report three cases with prenatally suspected CdLS based on the ultrasound findings as well as low PAPP‐A detected on first trimester screening in one case, and the results of the autopsy and the NIPBL gene mutation analysis. Copyright