Twelve years of assessing the quality of preimplantation genetic testing for monogenic disorders

Objective

Genomics Quality Assessment has provided external quality assessments (EQAs) for preimplantation genetic testing (PGT) for 12 years for eight monogenic diseases to identify sub-optimal PGT strategies, testing and reporting of results, which can be shared with the genomics community to aid optimised standards of PGT services for couples.

Method

The EQAs were provided in two stages to mimic end-to-end protocols. Stage 1 involved DNA feasibility testing of a couple undergoing PGT and affected proband. Participants were required to report genotyping results and outline their embryo testing strategy. Lymphoblasts were distributed for mock embryo testing for stage 2. Submitted clinical reports and haplotyping results were assessed against peer-ratified criteria. Performance was monitored to identify poor performance.

Results

The most common testing methodology was short tandem repeat linkage analysis (59%); however, the adoption of single nucleotide polymorphism-based platforms was observed and a move from blastomere to trophectoderm testing. There was a variation in testing strategies, assigning marker informativity and understanding test limitations, some clinically unsafe. Critical errors were reported for genotyping and interpretation.

Conclusion

EQA provides an overview of the standard of preimplantation genetic testing-M clinical testing and identifies areas of improvement for accurate detection of high-risk embryos.     

Influence of flow rate on transport of bacteriophage in shale saprolite

The objective of this study was to investigate the influence of flow rate on transport and retention of bacteriophage tracers in a fractured shale saprolite, which is a highly weathered, fine-grained subsoil that retains much of the fabric of the parent bedrock. Synthetic ground water containing PRD-1, MS-2, and bromide was passed through a saturated column of undisturbed shale saprolite at rates ranging from 0.0075 to 0.96 m d '. First arrival of the bacteriophage tracers in effluent samples in each of the experiments occurred within 0.01 to 0.04 pore volumes (PV) of the start of injection, indicating that bacteriophage were advectively transported mainly through fractures or macropores. Bacteriophage transport velocities, based on first arrival in the effluent, were very similar to fracture flow velocities calculated using the cubic law for flow in a fractured material. For MS-2, maximum concentration and mass of tracer recovered both increased steadily as flow rate increased. For PRD-1, these values initially increased, but were nearly constant at flow rates above 0.039 m d(-1), indicating that approximately 50% of the observed losses were independent of flow rate. Evaluation of the data indicates that physical straining and electrostatic or hydrophobic attachment to fracture or macropore walls were the dominant retention processes. Inactivation and gravitational settling playing secondary roles, except at the slowest flow rates. The study suggests that microbial contamination from sources such as septic fields and sewage ponds may pose a threat to the quality of ground water and surface water in areas with saprolitic subsoils.     

PLATE JUNCTIONS AND HYDROCARBON ACCUMULATIONS IN THE INDIAN REGION

This article relates the productive and potential oil fields in India to plate junctions and other major tectonic features. High geothermal gradients are known to accelerate the expulsion of petroleum from the source bed, as well as its migration and accumulation in favourable reservoir rocks, resulting in high yield. Some of the world's major petroleum deposits occur along ‘failed arms’ associated with the plume generated triple junctions. Seven triple junctions have been located in the Indian region, and two more are identified here. Interestingly, India's off-shore petroleum prospects coincide with some of these triple junctions. Cet article établit la relation entre les champs de pétrole en production et potentiels en Inde à la théorie des plaques et à d'autres traits tectoniques importants. L'on sait que des gradients géothermiques élevés accélèrent l'expulsion du pétrole à partir de la roche-mère et favorisent la migration et l'accumulation dans des réservoirs convenables. Quelques-uns des plus grands champs de pétrole du monde se rencontrent en liaison avec des ‘bras morts’ associés avec un système triple de fossés d'effondrement. Sept systèmes triples ont été repérés en Inde et deux autres sont reconnus ici. II est intéressant de remarquer que les possibilités pétrolières de l'offshore indien coïncide avec certains de ces systèmes triples. Este artículo establece la relación entre los campos petrolíferos en producción y potenciales de India a la teoría de placas y otros aspectos tectónicos. Es sabido que una gradiente térmica alta ascelera la expulsión del petróleo desde la roca madre y favorece su migración y acumulación en rocas reservorio favorables. Algunos de los mayores depósitos de petróleo se encuentran a lo largo de los “brazos muertos” asociados a un sistema triple de unión de placas. Siete uniones de este tipo habia sido localizadas en India y otros dos más son identificados aquí. Es interesante notar que las posibilidades petroleras en la zona marítima de India coinciden con alguna forma de sistemas triple de placas.