First-trimester screening for down syndrome with serum sampling at different gestational ages: the effect on screening performance

First trimester contingent screening for trisomies 21,18,13: is this model cost efficient and feasible in public health system?

PURPOSE

To evaluate the effectiveness of three different first trimester screening models for trisomies 21, 18 and 13, in terms of detection rate, invasive test rate and final costs.

MATERIAL AND METHODS

We analyzed the distribution of risk for trisomies 21, 18 and 13 in a population of 20,831 singleton pregnancies based on maternal age, fetal heart rate, nuchal translucency, free beta human chorionic gonadotropin and pregnancy-associated plasma protein A (Combined test). On the basis of our data, we estimated the performance and cost of screening for trisomies using three different models at specific cutoffs: Combined test; Cell free DNA test and Contingent screening test.

RESULTS

Using Combined test, DR for major trisomies was estimated to be 94.92%, invasive test rate was 6.3%. cfDNA would result in a DR of 97.92%, with an invasive test rate of 3.64%. Contingent screening approach would result in an overall DR of 97.82, with a rate for invasive procedure of 1.36% and a final cost lower than other screening policies (2,338,433 euro vs 5,796,060 of cfDNA and 2,385,473 of Combined test).

CONCLUSIONS

Contingent screening test could be a cost-efficient and feasible first trimester screening test for aneuploidies in public health system.

Screening for trisomy 18 using traditional combined screening vs. ultrasound-based protocol in tertiary center environment

OBJECTIVES

To compare the screening performances of combined screening test risk algorithm for trisomy 18 (T18) using various cutoffs with a multiparameter ultrasound-based method. To compare the general and maternal age (MA)-based screening performances for T18 by means of combined screening and an ultrasound-based method.

METHODS

This was a prospective, multicenter study based on a mixed-risk non-selected population of women referred to referral centers for a first-trimester screening. Each subject was offered a choice between either a traditional combined screening (CSG arm) or an ultrasound-based screening (USG arm). General and MA-based screening performances were measured.

RESULTS

The study population comprised 10 820 pregnancies as follows: 5132 in the CSG arm, including 28 cases of T18, and 5688 in the USG arm, including 29 cases of T18. In the CSG arm, the detection rate (DR) for T18 at a false-positive rate (FPR) of 3% was 86%, whereas the DR was 100% for the USG arm. MA influenced the T18 screening performance in the CSG arm and reduced the DR in MA ranges  <26 years and 31-35 years. This influence was not observed in the USG arm.

CONCLUSIONS

Only, a multiparameter ultrasound-based screening method may be considered an effective alternative to combined screening for T18 screening. The technique exhibits high and stable DRs irrespective of MA.

How Effective Is First-Trimester Screening for Trisomy 21 Based on Ultrasound Only?

Objective: To evaluate the most common first-trimester ultrasound features of fetuses with trisomy 21 (T21) and to examine the screening performance for Down syndrome (DS) using only ultrasound-based protocols. To investigate whether maternal age (MA) has an impact on the efficacy of the ultrasound-based screening methods. Methods: In a prospective study, 6,265 patients were examined. Two ultrasound-based risk calculation protocols were applied: ‘NT' (based on nuchal translucency) and ‘NT+' (based on NT and secondary markers). Results: A total of 5,696 patients were enrolled for analysis; 84 subjects with T21 were identified. Combinations of abnormal ultrasound markers were observed in only 1.2% of euploid fetuses compared to 71.5% of fetuses with T21. Among 17.9% of DS cases with cardiac anomaly, 14.3% comprised atrioventricular septal defects. For a false-positive rate of 3%, the detection rates of T21 were 73.8 and 91.7% for the ‘NT' and ‘NT+' protocols, respectively. The efficacy of both methods was affected by MA. Conclusions: Most of the fetuses with DS demonstrate a combination of ultrasound markers of aneuploidy in the first trimester. The ‘NT+' protocol is efficient and provides comparable performance as a combined screening test. It is a valuable method, especially when the access to biochemical analysis is restricted.