First-trimester screening for trisomy 21 with adjustment for biochemical results of previous pregnancies (original) (raw)

Prospective validation of first-trimester combined screening for trisomy 21

Ultrasound in Obstetrics and Gynecology, 2009

Objective To examine the performance of the new algorithm in screening for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) and maternal serum free β-human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein-A (PAPP-A).

Screening for fetal trisomy 21 in gestational weeks 6 and 7

Acta Obstetricia et Gynecologica Scandinavica, 2010

The objective was to examine the applicability of the two biochemical markers PAPP-A and free b-hCG for fetal trisomy 21 (T21) in very early pregnancy: gestational weeks (GA) 6 and 7. Medians for the two markers were generated on 36,745 fetal T21 unaffected pregnancies from gestational weeks 6-14. Concentrations were converted to Multiples of the Medians (MoMs). Median MoM from T21 affected pregnancies were compared over three intervals of gestational age; the very early weeks 6 and 7, weeks 8-10 and weeks 11-14. Median MoM from 9 affected pregnancies with a very early blood sample had a PAPP-A median MoM of 0.269, compared to 0.392 in weeks 8-10 and 0.531 in weeks 11-14. On the contrary, free b-hCG diverged from the median with increasing gestational age. Our data suggest that PAPP-A is a useful marker for very early testing in first trimester screening for fetal T21.

First-trimester combined screening for trisomy 21 at 7-14 weeks' gestation

Ultrasound in Obstetrics and Gynecology

In each case the patient-specific risk for trisomy 21 was estimated by multiplying the individual maternal age-related risk by the LR for fetal NT according to the mixture model8 and the combined LR for maternal serum free β-hCG and PAPP-A. Crude, standardized and model-based detection rates and false-positive rates were obtained by taking the proportion of cases with risks above a given risk threshold. The crude performance of screening refers to the observed values in our dataset. Standardized performance of screening was estimated after adjustments to take into account the maternal age distribution of pregnancies in England and Wales in 2000–20029. Model-based estimates of screening performance were derived by examining simulated data from 500 000 unaffected pregnancies and 500 000 trisomy 21 pregnancies with the maternal age distribution of pregnancies in England and Wales in 2000–2002, fetal NT distributions according to the mixture model and log MoM free β-hCG and log MoM PAPP...

First trimester intact hCG as an early marker of trisomy 21: a promise unrecognised?

Prenatal Diagnosis, 2008

Background An initial study of trisomy 21 cases showed that prior to 10 weeks, maternal serum levels of intact hCG in the early first trimester are lower than normal. Here we further study the levels prior to and after 10 weeks of gestation to further establish whether or not the intact hCG is effective as a very early screening marker.

Influence of first trimester biochemistry methodology on detection rate in screening for trisomy 21

Ginekologia Polska, 2017

Objectives: The purpose of the study was to compare detection rates (DR) of FMF-certified and non-certified biochemical tests (BC) in trisomy 21 screening at 11-13 + 6 weeks. Material and methods: In 2267 singleton pregnancies FMF-certified doctors measured crown to rump length (CRL) and nuchal translucency (NT). Serum samples were tested for free β-hCG and the PAPP-A using 2 analysers (Delfia-Perkin Elmer and Immulite 2000-DPC), the results were expressed in MoM values and used for computer calculation of the risk for trisomy 21. The cutoff value for the high trisomy 21 risk was 1:300. Results: Comparison of free β-hCG MoMs by DPC and Delfia demonstrated statistically significant differences in normal, and trisomy 21 fetuses respectively. Similarly, statistically significant differences were noted for PAPP-A MoMs. The above differences in MoMs resulted in altered sensitivity in screening for aneuploidy. The application of the FMF-certified method ensures a markedly higher DR = 74%, compared to non-certified tests (64%), both at 5% FPR. The ROC analysis was performed in order to assess the efficacy of both tests. Results of trisomy 21 BC + NT risk scales using the Delfia and DPC methods are highly significant (p < 0.0001), which means that their discrimination ability is > 90%. The difference between results obtained using the Delfia and DPC methods is AUC = 0.0150 and is statistically significant (Z = 2.4728, p = 0.0134). Conclusions: The use of FMF-certified first trimester biochemistry analysers improves DR for trisomy 21. The use of non-certified analysers causes reduction of DR and an increase of invasive procedure rate.