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n Obstetrics and Gynaecology Forum - Appropriate clinical use of non-invasive prenatal testing in South Africa : review
Non-invasive prenatal testing (NIPT) refers to testing of cell-free fetal DNA in the maternal plasma, and is currently a rapidly evolving field. NIPT has recently become accepted as a screening test for certain aneuploidies, in particular Down syndrome (DS). NIPT testing is available in South Africa, although the genomic and bioinformatic processing of samples is performed elsewhere (most commonly the USA).
Several different approaches to NIPT testing are available, each with specific advantages and disadvantages. They all have a high sensitivity and specificity for detection of DS, but may be less accurate for other aneuploidies. Even for DS, NIPT is not a diagnostic test: some cases of DS will be missed, and positive results must be confirmed with an invasive test.
NIPT is indicated for screening for DS, especially in women at increased prior risk. Its role in testing for other aneuploidies, such as trisomy 13 or Turner syndrome, is less clear. NIPT is contraindicated where the fetus is at risk for a broader range of chromosome abnormalities - in this case invasive testing for karyotype should be offered.
The availability of NIPT is limited mainly by cost and the fact that it is not a medical aid benefit - it is currently for those who can afford to pay for it out of pocket.
In general an NIPT test can be performed from 10 weeks gestation, has a turn-around time of up to 2 weeks, and a failure rate of ~5%. Ideally, NIPT should be integrated into a broader Fetal Medicine service, and we present several options. NIPT should be offered in the context of genetic counselling. NIPT has potential value for O&G practices in more isolated geographical settings, but the practical and counselling pitfalls are significant.
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