Multiple displacement amplification as the first step can increase the diagnostic efficiency of preimplantation genetic testing for monogenic disease for β-thalassemia

Clinical outcomes following preimplantation genetic testing for monogenic conditions: a systematic review of observational studies

OBJECTIVE

We aimed to report a summary of clinical outcomes following preimplantation genetic testing for monogenic conditions, by performing a systematic review of published literature on clinical pregnancy and live birth rates following preimplantation genetic testing due to a monogenic indication. Additionally, we aimed to undertake a subgroup analysis of clinical outcomes of concurrent monogenic and aneuploidy screening.

DATA SOURCES

Three electronic databases (MEDLINE, EMBASE, and PubMed) were searched from inception to May 2024.

STUDY ELIGIBILITY CRITERIA

Quantitative data audits, observational studies, and case series reporting clinical outcomes for individuals undergoing preimplantation genetic testing for a monogenic indication were included. Only studies using blastocyst biopsies with polymerase chain reaction-based or genome-wide haplotyping methods for molecular analysis were eligible to reflect current laboratory practice.

METHODS

Quality assessment was performed following data extraction using an adaptation of the Joanna Briggs critical appraisal tool for case series. Results were extracted, and pooled mean clinical pregnancy rates and birth rates were calculated with 95% confidence intervals (95% CI). We compared outcomes between those with and without concurrent preimplantation genetic testing for aneuploidy.

RESULTS

Our search identified 1372 publications; 51 were eligible for inclusion. Pooled data on 5305 cycles and 5229 embryo transfers yielded 1806 clinical pregnancies and 1577 births. This translated to clinical pregnancy and birth rates of 34.0% [95% CI: 32.8%-35.3%] and 29.7% [95% CI: 28.5%-31.0%] per cycle and 24.8% [95% CI: 23.6%-26.0%] and 21.7% [95% CI: 20.8%-23.1%] per embryo transfer. In studies with concurrent aneuploidy screening, clinical pregnancy and birth rates were 43.3% [95% CI: 40.2%-46.5%] and 37.6% [95% CI: 34.6%-40.8%] per cycle and 37.0% [95% CI: 33.9%-40.3%] and 31.8% [95% CI: 28.8%-35.0%] per embryo transfer. Studies without aneuploidy screening reported clinical pregnancy and birth rates of 32.5% [95% CI: 31.0%-34.1%] and 28.1% [95% CI: 26.6%-29.7%] per cycle and 21.2% [95% CI: 19.8%-22.6%] and 18.6% [95% CI: 17.3%-20.0%] per embryo transfer.

CONCLUSION

This systematic review reveals promising clinical outcome figures for this indication group. Additionally, synthesizing the published scientific literature on clinical outcomes from preimplantation genetic testing for monogenic conditions provides a rigorous, noncommercial evidence base for counseling.

Evaluating the application value of NGS-based PGT-A by screening cryopreserved MDA products of embryos from PGT-M cycles with known transfer outcomes

PURPOSE

To determine the application value of next-generation sequencing (NGS)-based preimplantation genetic testing for aneuploidies (PGT-A).

METHODS

We conducted a retrospective case-control study on a cohort of frozen-thawed embryo transfer (FET) cycles following preimplantation genetic testing for monogenic disorders (PGT-M) between 2014 and 2017. Cycles that produced live births or early miscarriages were divided into live birth group (n = 76) or miscarriage group (n = 19), respectively. The NGS-based aneuploidy screening was performed on the multiple displacement amplification (MDA) products of the embryonic trophectoderm biopsy samples that were cryopreserved following PGT-M.

RESULTS

In the live birth group, 75% (57/76) embryos were euploid and 14.5% (11/76) were aneuploid. The remaining 10.5% (8/76) embryos were NGS-classified mosaic with the high- (≥ 50%) and low-level (< 50%) mosaicism rates at 7.9% (6/76) and 2.6% (2/76), respectively. In the miscarriage group, only 23.5% (4/17) embryos were aneuploid, while 58.8% (10/17) were euploid and 17.6% (3/17) were NGS-classified mosaic with the high- and low-level mosaicism rates at 11.8% (2/17) and 5.9% (1/17), respectively. For live birth and miscarriage groups, the transferable rate was 82.9% (63/76) and 70.6% (12/17), respectively, whereas the untransferable rate was 17.1% (13/76) and 29.4% (5/17), respectively.

CONCLUSION

The application of NGS-based PGT-A remains questionable, as it may cause at least one in six embryos with reproductive potential to be discarded and prevent miscarriage in less than one in three embryos in single-gene disease carriers.

Long-read sequencing on the SMRT platform enables efficient haplotype linkage analysis in preimplantation genetic testing for β-thalassemia

PURPOSE

This study aimed to evaluate the value of long-read sequencing for preimplantation haplotype linkage analysis.

METHODS

The genetic material of the three β-thalassemia mutation carrier couples was sequenced using single-molecule real-time sequencing in the 7.7-kb region of the HBB gene and a 7.4-kb region that partially overlapped with it to detect the presence of 17 common HBB gene mutations in the Chinese population and the haplotypes formed by the continuous array of single-nucleotide polymorphisms linked to these mutations. By using the same method to analyze multiple displacement amplification products of embryos from three families and comparing the results with those of the parents, it could be revealed whether the embryos carry disease-causing mutations without the need for a proband.

RESULTS

The HBB gene mutations of the three couples were accurately detected, and the haplotype linked to the pathogenic site was successfully obtained without the need for a proband. A total of 68.75% (22/32) of embryos from the three families successfully underwent haplotype linkage analysis, and the results were consistent with the results of NGS-based mutation site detection.

CONCLUSION

This study supports long-read sequencing as a potential tool for preimplantation haplotype linkage analysis.

Predictive Prenatal Diagnosis for Infantile-onset Inflammatory Bowel Disease Because of Interleukin-10 Signalling Defects

OBJECTIVES

Advances in genetic technologies provide opportunities for patient care and ethical challenges. Clinical care of patients with rare Mendelian disorders is often at the forefront of those developments. Whereas in classical polygenic inflammatory bowel disease (IBD), the predictive value of genetic variants is very low, predictive prenatal genetic diagnosis can inform families at high risk of severe genetic disorders. Patients with IL-10 signalling defects because of pathogenic variants in IL10RA, Il10RB, and IL10 develop severe infantile onset inflammatory bowel disease that is completely penetrant and has a high morbidity and substantial mortality despite treatment.

METHODS

We performed a survey among tertiary specialist paediatric centers of 10 countries on the utilization of predictive prenatal genetic diagnosis in IL-10 signalling defects. We retrospectively report prenatal genetics in a series of 8 families.

RESULTS

International variation in legislation, guidelines, expert opinion, as well as cultural and religious background of families and clinicians results in variable utilization of preimplantation and prenatal genetic testing for IL-10 signalling defects. Eleven referrals for prenatal diagnosis for IL-10 signalling defects were identified across 4 countries. We report on 8 families who underwent prenatal preimplantation monogenic testing after in vitro fertilization (n = 2) and/or by amniocentesis/chorion villus sampling (n = 6). A genetic diagnosis was established in 1 foetus and excluded in 7 foetuses (all IL10RA variants).

CONCLUSIONS

Prenatal genetic testing for IL10R-defects is feasible, yet the legal and ethical considerations are complex and controversial. In some countries, predictive genetics for IL-10-related signalling defects is entering clinical practice.

Factors affecting Thai pregnant women's decisions concerning prenatal diagnosis and termination of pregnancy for β-thalassemia

AIM

To investigate the factors influencing decisions concerning prenatal diagnosis (PND) and termination of pregnancy for β-thalassemia in Thai pregnant women.

METHODS

A total of 142 Thai Buddhist pregnant women waiting for PND were asked to undertake semi-structured interviews regarding their reasons for PND and their decisions and reasoning concerning pregnancy if the fetus was found to be affected. The interviews were analyzed using a thematic content approach.

RESULTS

Thai pregnant women accepted PND for three reasons: to know whether their pregnancies were affected, to confirm that their pregnancies were unaffected and to terminate if their pregnancies were affected. Three decisions identified among the women were to terminate the pregnancy, to continue the pregnancy and undecided. The interview analysis identified five themes and nine sub-themes affecting pregnancy-related decision-making: (i) quality of life (suffering or no disability); (ii) burden (difficulty or acceptability); (iii) sense of motherhood (the best way for the child or I cannot hurt my child); (iv) significant others (support to terminate, support to continue or support to wait for the test result) and (v) conflict in deciding.

CONCLUSION

An acceptance of PND in Thai pregnant women was not always associated with pregnancy termination. Multiple factors influenced the decision to terminate, but not their religious affiliation.