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First-trimester screening for trisomy 21 combining biochemistry and ultrasound at individually optimal gestational
Antoni Borrell1, Elena Casals, Albert Fortuny
1Prenatal Diagnosis Unit, Institute of Gynecology, Obstetrics and Neonatology, Hospital Clinic, University of Barcelona Medical School, Barcelona, Catalonia, Spain. aborrell@medicina.ub.es
Insights
The Combined Test effectively screens for Down syndrome (trisomy 21) in early pregnancy. This prenatal screening method achieved an 88% detection rate with a low false-positive rate.
Area of Science:
- Prenatal diagnostics
- Maternal-fetal medicine
- Genetics
Background:
- Prenatal screening for chromosomal abnormalities is crucial for expectant mothers.
- The Combined Test integrates biochemical markers and ultrasound for improved detection rates.
Purpose of the Study:
- To evaluate the efficacy of the Combined Test for prenatal detection of trisomy 21.
- To assess a novel timing strategy for first-trimester screening.
Main Methods:
- Maternal serum samples analyzed for pregnancy-associated plasma protein-A and free-beta hCG between 7-12 weeks.
- Fetal nuchal translucency and gestational age assessed via ultrasound between 10-14 weeks.
- Combined risk calculated and communicated same-day; chorionic villus sampling offered for risks >= 1:250.
Main Results:
- Study included 2780 pregnancies with complete follow-up.
- Observed detection rate for trisomy 21 was 88%; for trisomy 18, it was 75%.
- A false-positive rate of 3.3% was recorded.
Conclusions:
- The Combined Test demonstrates high effectiveness in detecting trisomy 21 during the first trimester.
- Optimized timing for biochemical and ultrasound assessments significantly reduces false positives.
Objective:
To assess the effectiveness of the Combined Test in the prenatal detection of trisomy 21 in the general pregnant population using a new timing for the screening approach.
Methods:
First-trimester maternal serum biochemical markers (pregnancy-associated plasma protein-A and free-beta hCG) were determined in maternal serum at 7 to 12 weeks. Fetal nuchal translucency and gestational age were assessed at the 10- to 14-week ultrasound scan. A combined risk was estimated and delivered to the women the same day. When the risk was 1:250 or above, chorionic villus sampling was offered.
Results:
Mean gestational age at biochemistry was 9.4 weeks, being 12.3 at ultrasound. In the 2780 studied pregnancies with a complete follow-up, observed detection rates were 88% (7/8) for trisomy 21 and 75% (3/4) for trisomy 18, with a 3.3% (92/2765) false-positive rate.
Conclusion:
The Combined Test, assessing biochemistry and ultrasound at individually optimal ages in the first trimester, showed an 88% detection rate for trisomy 21 with a remarkably reduced false-positive rate (3.3%).
