Testing for some genetic abnormalities in embryos on hold at NUH centre after recall of test kit

Testing for some genetic abnormalities in embryos on hold at NUH centre after recall of test kit

SINGAPORE: The Pre-Implantation Genetic Diagnosis (PGD) Centre at the National University Hospital (NUH) has stopped testing for some genetic defects in embryos as a precaution.

Responding to Channel NewsAsia’s queries, the Centre, which receives and tests genetic materials from seven In Vitro Fertilisation (IVF) facilities in Singapore, said it did so after the manufacturer of a test kit it uses to conduct such tests issued a worldwide recall for its product and stopped shipments. 

The Centre said Illumina, the manufacturer of the affected 24sure+ microarray kit, which tests for chromosomal problems, notified it of a worldwide recall of the test kit on May 10.

According to the Centre, the test kit was recalled by the company due to a “detection issue involving a small area of chromosome 3”. 

The Centre’s Director, Assoc Prof Samuel Chong, said failure to detect this part of chromosome 3 could result in failure of the embryo to implant, miscarriages or births with congenital malformations or other abnormalities.

The pause on testing is temporary, as the Centre is sourcing for alternative test kits.

ONLY ONE OF TWO TYPES OF PGD TESTING AFFECTED BY RECALL

According to information on NUH’s Women’s Centre website, pre-implantation genetic diagnosis is done during the IVF process to test embryos for inherited genetic disorders, before they are transferred to the uterus. 

The testing of embryos means a decreased risk of a couple with “serious inherited disorders” passing them on to their child. The screening is also meant for couples who have experienced multiple miscarriages due to suspected genetic disorders. 

According to reports, about 130 PGD cycles were performed at the PGD Centre for more than 25 genetic diseases between 2005 and 2015. The Centre said it performs two types of PGD testing.

The Polymerase Chain Reaction (PCR)-based testing is to screen for mutations in single genes, which results in disorders such as fragile X syndrome, haemophilia A and thalassaemia. 

The aCGH-based PGD testing screens for chromosomal translocations, and Prof Chong said it is testing for this abnormality that has been temporarily halted. He said testing for single-gene mutations has not been affected. 

“To date, there have been no reported cases of birth with an abnormality due to chromosomal imbalance in the specific region of chromosome 3 in Singapore or worldwide,” Prof Chong said. 

He added that Illumina got in touch in June to say that the detection failure was confined to a region in that chromosome, but others were not affected.

PGD test kit illumina
A screenshot of Illumina's website saying it would discontinue the test kit used to test embryos for some genetic abnormalities. 

So while the test is still able to detect abnormalities in the structure of other chromosomes, Prof Chong said it was halted because Illumina stopped all shipments of the kit, and instructed the Centre not to use any available kits. 

Illumina’s investigations to determine the timeline of the defects of the test kit are ongoing. 

NO PGD PATIENTS IN SINGAPORE DIRECTLY AFFECTED

The Centre has informed all seven partner Assisted Reproduction Technology (ART) centres.

Prof Chong said 39 of 44 patients who used the test kit to screen for “various chromosomal abnormalities” since 2011 were contactable, and have been informed of the recall.

The ART centres have counselled them “of their available options”. 

He said the PGD Centre is continuing to reach out to the rest of the patients.

Channel NewsAsia understands none of the patients who used the test kits were being tested for the specific region of chromosome abnormalities affected by the halting of tests.

When contacted, Illumina said they were informed by a customer that the test kit had not picked up an abnormality on the affected chromosome.

A notice on its website read that the test kit was discontinued on Oct 12. The company said it does not have an alternative solution for the test kit.
 

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