In this episode of The Good GP, host Dr Krystyna de Lange is joined by Dr Alison Archibald, a Certified Genetic Counsellor at the Victorian Clinical Genetic Services, to discuss noninvasive prenatal testing (NIPT).
NIPT is a screening test that looks at small pieces of DNA in the maternal blood to identify chromosome conditions in the foetus. This test can be done from about 10 weeks gestation onwards, and it can detect conditions like Down syndrome, trisomy 18, and trisomy 13. It can also determine foetal sex and screen for a wider range of chromosome conditions through genome-wide NIPTs.
Dr Archibald explains that NIPT can be offered to all pregnant women, but it's important to understand that it is a screening test and not diagnostic. False positive and false negative results can occur due to the analysis of placental DNA instead of foetal DNA. Diagnostic tests like amniocentesis should be offered to confirm any chromosome conditions indicated by NIPT. Furthermore, NIPT does not detect genetic conditions caused by smaller changes in DNA or single gene conditions.
The discussion also touches on the differences between NIPT and combined first trimester screening (CFTS). While NIPT is a more advanced screening test with higher sensitivity and lower specificity, CFTS is still a good alternative if the cost of NIPT is a concern. It is important for patients having NIPT to also undergo the 12-13 week ultrasound to assess foetal anatomy. Dr Archibald emphasises the significance of offering the ultrasound alongside NIPT to avoid missing any foetal abnormalities early on.
In terms of counselling patients about NIPT, Dr Archibald suggests explaining that it is a screening test with false positive and false negative results. Patients should be aware of the limitations of NIPT and understand what it does not cover. It is important to discuss the need for diagnostic tests if NIPT indicates an increased chance of a chromosome condition. Ultimately, the goal is to provide patients with comprehensive information about NIPT so they can make informed decisions.
Resources mentioned in this episode:
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