First-trimester combined screening for trisomy 21 at 8-13 weeks (original) (raw)
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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).
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...
Two-stage first-trimester screening for trisomy 21 by ultrasound assessment and biochemical testing
Ultrasound in Obstetrics and Gynecology, 2010
K E Y W O R D S: ductus venosus flow; nasal bone; nuchal translucency; screening for trisomy 21; tricuspid regurgitation ABSTRACT Objectives This study was carried out to examine the performance of a contingent policy in first-trimester screening for trisomy 21, in which the estimated risk was first derived by a combination of maternal age, fetal nuchal translucency (NT) thickness, presence/absence of the nasal bone, blood flow in the ductus venosus or flow across the tricuspid valve, and biochemical testing was carried out only in those who were found to have an intermediate risk. We also examined the performance of a policy in which the estimated risk was first derived by a combination of maternal age and biochemical testing, and ultrasound examination was carried out only in those with an intermediate risk.
First Trimester Biochemical Screening for Trisomy 21
Annals of Clinical Biochemistry: An international journal of biochemistry and laboratory medicine, 1995
The potential efficacy of screening for trisomy 21 in the first trimester, using maternal serum markers 01 fetoprotein, free fJ human chorionic gonadotropin, unconjugated oestriol and pregnancy associated plasma protein A, was studied in an unselected population of women between the seventh and fourteenth week of gestation. Using a combination of 01 fetoprotein and free fJ human chorionic
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.
Ultrasound in Obstetrics and Gynecology, 2002
Objective To evaluate the performance of a one-stop clinic for assessment of risk (OSCAR) for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness and maternal serum free β -human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11-14 weeks of gestation. Method Screening for trisomy 21 was carried out by OSCAR in 15 030 singleton pregnancies with live fetuses at 11-14 weeks. The estimated risk for trisomy 21 was calculated, and the women were counseled regarding this risk and the option of invasive testing or expectant management. Follow-up of the outcome of all pregnancies was carried out. The detection and false-positive rates for different risk cut-offs were calculated. Results Fetal NT and maternal serum free β -hCG and PAPP-A were successfully measured in all cases. Pregnancy outcome, including karyotype results or the birth of a phenotypically normal baby, was obtained from 14 383 cases. The median maternal age of these cases was 34 (range 15-49) years and in 6768 (47.1%) the age was 35 years or greater. The median gestation at screening was 12 (range 11-14) weeks and the median fetal crown-rump length was 64 (range 45-84) mm. The estimated risk for trisomy 21 based on maternal age, fetal NT and maternal serum free β -hCG and PAPP-A was 1 in 300 or greater in 6.8% (967 of 14 240) normal pregnancies, in 91.5% (75 of 82) of those with trisomy 21 and in 88.5% (54 of 61) of those with other chromosomal defects. For a fixed false-positive rate of 5% the respective detection rates of screening for trisomy 21 by maternal age alone, maternal age and serum free β -hCG and PAPP-A, maternal age and fetal NT, and by maternal age, fetal NT and maternal serum biochemistry were 30.5%, 59.8%, 79.3% and 90.2%, respectively. Conclusion Screening for trisomy 21 by a combination of maternal age, fetal NT and maternal serum biochemistry at 11-14 weeks can be provided in an OSCAR setting and is associated with a detection rate of about 90% for a false-positive rate of 5%.