1. Non Invasive Prenatal Testing for Aneuploidy (NIPT)
Max Brinsmead MB BS PhD
December 2017

2. How is it done?
Cell-free DNA from fetal trophoblast is released into the maternal circulation
Detected from 10w gestation until delivery
Amplified by massive parallel sequencing
Quantified by comparing amounts of DNA from chromosomes of interest esp C21
Complex biostatistical analysis of the amount detected in comparison to fetal DNA from other chromosomes
Results in a low or high risk result
So this is a SCREENING TEST

3. How good is the test?
From a meta analysis of31 studies and >148,00 tests for Trisomy 21
Trisomy 21 Sensitivity 99.4% Specificity 99.9%
Trisomy 18 Sensitivity 97.7% Specificity 99.9%
Trisomy 13 Sensitivity 90.6% Specificity 100%
Monosomy X Sensitivity 92.9% Specificity 100%
Not recommended for Twins

4. Advantages & Problems of NIPT
Non invasive and therefore “safe”
False positives and Inconclusive Results for 2 – 6% of samples. Possible reasons include:
Low fraction of fetal DNA in the sample
Vanishing twin with aneuploidy
Placental mosaicism (a problem for CVS too)
Maternal chromosomal problems and cancers
Up to 20% of inconclusive results will be inconclusive on re sampling and testing
Issues of QA in commercial labs
Cost
Loss of opportunity/skills in CVS and amnio
Ethical issues (to be discussed)

5. Ethical Problems of NIPT
Because it is a SCREENING TEST all of the implications have to be known and understood before the test is done
Some fetal aneuploidies, especially those of the sex chromosomes, have unpredictable effects and outcomes
A maternal chromosomal abnormality can be revealed
Some maternal cancers can be revealed
Cost effectiveness and its role in high risk and the general obstetric population are yet to be determined

6. Any Questions or Comments?
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