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Published on: February 21, 2015
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Clinical experience with single-nucleotide polymorphism-based non-invasive prenatal screening for 22q11.2 deletion
S J Gross1, M Stosic1, D M McDonald-McGinn2
1Natera Inc, San Carlos, CA, USA.
Summary
This study evaluated a SNP-based non-invasive prenatal test (NIPT) for 22q11.2 deletion syndrome, finding a low positive predictive value but identifying cases in a referral population. Management resources are crucial for high-risk pregnancies.
Area of Science:
- Genetics
- Prenatal Diagnostics
- Reproductive Health
Background:
- 22q11.2 deletion syndrome is a common genetic disorder.
- Non-invasive prenatal testing (NIPT) offers a safer alternative to traditional prenatal screening.
- SNP-based NIPT is a newer approach for detecting microdeletion syndromes.
Purpose of the Study:
- To assess the clinical performance of SNP-based NIPT for 22q11.2 deletion syndrome.
- To evaluate clinical follow-up and patient decisions after high-risk NIPT results.
- To determine the positive predictive value (PPV) of this NIPT method in a clinical setting.
Main Methods:
- A cohort of 21,948 samples was screened using SNP-based NIPT for 22q11.2 deletion.
- Clinical follow-up was performed for all high-risk cases.
- Diagnostic testing and ultrasound findings were correlated with NIPT results.
Main Results:
- Ninety-five high-risk results were reported, with a PPV of 18.0% (11 true positives, 50 false positives).
- Invasive testing was pursued by 57.1% of high-risk cases.
- Ultrasound anomalies were more frequent in true-positive cases (81.8%) compared to false positives (18.0%).
- Two cases of maternal 22q11.2 deletion were identified.
- Three pregnancy terminations occurred, two confirmed as true positives.
Conclusions:
- SNP-based NIPT for 22q11.2 deletion syndrome has a frequency of about 1 in 1000 in the referral population.
- The test can identify most affected fetuses, but requires careful interpretation due to its PPV.
- Availability of genetic counseling and management resources is essential for high-risk pregnancies identified by NIPT.
