Clinical Practice Guidelines for Prenatal Aneuploidy Screening and Diagnostic Testing from Korean Society of Maternal-Fetal Medicine: (1) Prenatal Aneuploidy Screening

The value of combined detailed first-trimester ultrasound-biochemical analysis for screening fetal aneuploidy in the era of non-invasive prenatal testing

PURPOSE

This study aimed to investigate the performance, cost-effectiveness and additional findings of combined detailed ultrasound and biochemical screening for risks of major fetal trisomies in the first-trimester.

METHODS

This is a retrospective analysis study, we estimated the risk of trisomies 21, 18 and 13 based on maternal age, fetal nuchal translucency thickness, nasal bone, ductus venosus pulsatility index velocity, tricuspid regurgitation, fetal heart rate, free beta-human chorionic gonadotropin, and pregnancy-associated plasma protein A in singleton pregnant women, and performed non-invasive prenatal testing for women with risks of trisomy 21 between 1:500 and 1:300. Invasive diagnostic testing was performed for women with positive or failed non-invasive prenatal testing result and in the high-risk group of this screening method. The direct costs were compared between this strategy and the non-invasive prenatal testing which alone used as first-line screening for all pregnant women.

RESULTS

Among 25,155 singleton pregnant women who underwent screening, 24,361 were available for analysis, of these, 194 cases underwent non-invasive prenatal testing. Among the 24,361 women, 39, 19, and 7 had trisomies 21, 18 and 13, respectively. The use of this strategy could potentially detect approximately 94.87% of trisomy 21 cases, 100% of trisomy 18 cases, and 100% of trisomy 13 cases, with false-positive rates of 2.49%, 0.41%, and 0.49%, respectively. The overall detection rate and overall false-positive rates were 96.92% and 2.52%, respectively. The detection rate was 100% in the advanced age group and 94.12% in the general age group. Additionally, structural abnormalities were detected in 137 fetuses, and 44 fetuses had other chromosomal abnormalities. The total cost of this strategy was $3,730,843.30, and the cost per person tested was $153.15. The total cost of using non-invasive prenatal testing as the first-line strategy would be $6,813,387.04 and the cost per person tested was $279.68.

CONCLUSIONS

Our strategy is an efficient and cost-effective approach for detecting major trisomies and identifying more fetuses with a potential abnormality. Therefore, this strategy is a valuable screening method and highly feasible in the clinical setting.

Diagnostic value of maternal alpha-fetoprotein variants in second-trimester biochemical screening for trisomy 21 and 18

To evaluate the clinical predictive value of serum alpha-fetoprotein variants (AFP-L2, AFP-L3) in combination with maternal serum prenatal screening biomarkers in predicting fetal trisomy 21 and trisomy 18. We analyze the data of singleton pregnant women at 15–20⁺⁶ weeks of 731,922 gravidas from October 2007 to September 2019. The research objects were separated into the following groups: control (n = 569), trisomy 21 (n = 116), and trisomy 18 (n = 52). The cases were diagnosed by chromosomal karyotypic analysis of amniotic fluid cells. Level of AFP-L2 and AFP-L3 were detected in maternal serum among control women and patients. Receiver operator characteristic analysis, detection rate, false positive rate, false negative rate, positive predictive value, negative predictive value, positive likelihood ratio and negative likelihood ratio, comprehensive discriminant improvement, net weight classification improvement, decision curve analysis and Hosmer–lemeshow (H-L) test were used to investigate the predictive value of free β-hCG, AFP, AFP-L2 and AFP-L3 on the risk models of trisomy 21, 18. There was a statistically significant difference in maternal serum AFP-L2 and AFP-L3 multiple of the median (MoM) among the trisomy 21, trisomy 18, and control groups. The AUCs of AFP-L2 and AFP-L3 for the screening trisomy 21 and trisomy 18 fetus were 0.785, 0.758 and 0.775, 0.754. According to ROC, the optimal cut-off values of AFP-L2 and AFP-L3 for predicting trisomy 21 and trisomy 18 fetuses all were 1.09 MoM and 1.30 MoM, respectively. The risk-calculation model constructed by AFP-L2 + AFP-L3 MoM manifested better efficiency than the original single-value truncation method using AFP MoM alone. Compared with different modeling methods, the AUC of trisomy 21 fetuses predicted by AFP-L2 + AFP-L3 + free β-hCG achieved an optimal value (0.938), while the AUC of trisomy 18 fetus predicted by AFP-L2 + free β-hCG was the best (0.991). Compared with AFP, the IDI of AFP-L2 or AFP-L3 alone increased 9.56% and 12.34%; the NRI increased 26.50% and 26.70 in predicting trisomy 21. For trisomy 18, the IDI of AFP-L2 or AFP-L3 alone declined with 8.12% and 1.52%; the NRI declined with 13.84% and 8.54%. In the combined model, the model with best detection rate, false positive rate and positive likelihood ratio was AFP-L2 + AFP-L3 + free β-hCG, followed by AFP-L2 + free β-hCG and AFP-L3 + free β-hCG, and finally AFP + free β-hCG. Maternal serum AFP-L2 and AFP-L3 in the second trimester is a good marker for screening trisomy 21 and trisomy18 with high sensitivity and specificity. The combined screening results are better than the single marker, and the efficiency of AFP-L2 + AFP-L3 + free β-hCG is the best.