Appropriate biochemical parameters in first-trimester screening for Down syndrome

Cuckle, Howard; Lith, J. M. M. van

doi:10.1002/(sici)1097-0223(199906)19:6<505::aid-pd572>3.0.co;2-6

Cited by 142 publications

(83 citation statements)

References 38 publications

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“…The second procedure is to use a meta-analysis approach in which data from the literature on all published series are included to derive parameter estimates; 14,15 these may then be tailored to an individual centre's own population and laboratory conditions using procedures derived for the second trimester. 14 Although this latter approach enables population parameters to be calculated from much larger series of Down's syndrome cases than is possible with most direct measurement series, the problem of temporal variation in median shifts has not been fully addressed.…”

Section: Discussionmentioning

confidence: 99%

The effect of temporal variation in biochemical markers of trisomy 21 across the first and second trimesters of pregnancy on the estimation of individual patient-specific risks and detection rates for Down's syndrome

Spencer

Crossley²,

Aitken³

et al. 2003

Ann Clin Biochem

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Background In a previous study we examined the changes in the median multiple of the median (MoM) with gestation of free beta human chorionic gonadotrophin (FbhCG), total human chorionic gonadotrophin (ThCG), a-fetoprotein (AFP) and pregnancy-associated plasma protein A (PAPP-A) in a large series of Down's syndrome pregnancies. Results showed that there was a significant temporal variation of the MoM for each marker. In this paper, we assess the impact of this temporal shift on the estimation of patient-specific risks and the detection rates (DRs) for Down's syndrome pregnancies.

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Section: Discussionmentioning

confidence: 99%

The effect of temporal variation in biochemical markers of trisomy 21 across the first and second trimesters of pregnancy on the estimation of individual patient-specific risks and detection rates for Down's syndrome

Spencer

Crossley²,

Aitken³

et al. 2003

Ann Clin Biochem

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“…Spencer et al 16 retrospectively analysed FhhCG and PAPP-A in stored serum from 210 Down's Syndrome pregnancies and when these data were combined with NT measurements in the same series of pregnancies 12,17 a detection rate of 89% at a 5% false positive rate was obtained -close to the modelled detection rates of 80 -87% predicted for the combined test in other studies 18,19 . Similar results have been reported in other smaller retrospective studies of combined ultrasound and biochemical (CUB) screening 20 , but there is relatively little information on the prospective performance of such screening in the general pregnant population.…”

Section: Introductionmentioning

confidence: 53%

Combined ultrasound and biochemical screening for Down's Syndrome in the first trimester: a Scottish multicentre study

Crossley¹

2002

BJOG: An International Journal of Obstetrics and Gynaecology

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Objective To evaluate the use of ultrasound measurements of fetal nuchal translucency (NT) obtained in a routine antenatal clinic setting in combination with appropriate biochemical markers as a first trimester screening test for Down's Syndrome. Design Multicentre observational study.Setting Fifteen Scottish maternity units.Population Pregnant women (n ¼ 17,229) attending routine antenatal clinics at 10 -14 weeks of gestation.Methods NT measurements were attempted in all women along with the measurement of maternal serum free beta human chorionic gonadotrophin (FhhCG) and pregnancy-associated plasma protein-A (PAPP-A). All results were converted to multiples of the appropriate gestational median (MoM) and using a statistical model the risk of an affected pregnancy was derived. No results were given to participating women but all were offered routine second trimester biochemical screening. All cases of Down's Syndrome within the study group were ascertained and the detection rate for each marker was estimated. Main outcome measures Success rate of obtaining NT measurements and overall effectiveness of ultrasound and biochemical markers individually and in combination for the detection of Down's Syndrome pregnancies. Results NT measurements were obtained in 72.9% of women and blood samples in 98.4%. Forty-five cases of Down's Syndrome were ascertained (2.6/1000). NT measurements were obtained in 37 cases (median NT 1.65 MoM), blood samples in 42 cases and both NT and blood in 34 cases. In combination with the a priori maternal age risk, observed detection rates at a 5% false positive rate were 20/37 (54%) for NT, 23/42 (55%) for FhhCG and PAPP-A and 28/34 (82%) for a combination of NT, FhhCG and PAPP-A using a cutoff risk of 1:250. The effect of failing to obtain NT measurements in all cases reduces the overall detection rate to 62% (i.e. 28/45) if the entire series of affected pregnancies within the study group is considered. Conclusions NT in combination with appropriate serum markers has the potential to detect over 80% of Down's Syndrome fetuses in early pregnancy. However, NT measurement is highly operator-dependent. It requires training, external quality control and adequate time to allow accurate measurement, otherwise suboptimal performance will result.

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“…From a methodological point of view, during the first period of the study Down syndrome was screened by a one-step protocol, with blood taken for maternal biochemistry the same day the ultrasound was performed. Published experiences 4,[28][29][30] and our own results have demonstrate a higher efficiency when biochemistry and ultrasound are assessed at individually established optimal gestational ages. As suggested by Spencer et al, screening algorithms modified to take account of the significant temporal variation in the screening markers should allow more accurate gestation-specifics risks.…”

Section: Discussionmentioning

confidence: 70%

Impact of Ductus Venosus Assessment in Screening Down Syndrome Protocols: An Improved Strategy in a Fetal Medicine Unit

Echevarría¹,

Comas²,

Rodríguez³

et al. 2009

Donald School Journal of Ultrasound in Obstetrics and Gynecology

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Objective: To estimate the improvement in screening efficiency when ductus venosus (DV) Doppler studies are added to existing Down syndrome (DS) screening protocols.Methods: First-trimester combined screening for trisomy 21 was prospectively carried out, from October 2003 to March 2008, in 8842 consecutive singleton pregnancies attended in our tertiary reference center. The nuchal translucency (NT) and the pulsatility index for veins for DV were calculated. The maternal serum biochemistry was measured using the Kryptor analyzer, at the same time of the scan (one step strategy) or before it (two step strategy). The detection rate (DR) and false-positive rates for standard screening strategy (maternal age, NT and biochemistry) and the same strategy but including DV assessment were calculated.Results: Successful DV assessment was possible in the 95.3% of cases, representing a total of 8426 cases. Down syndrome was identified in 34 pregnancies (prevalence of DS 1:250). For a fixed screen positive rate of 5%, the addition of the DV assessment improves the DR from 85 to 94% and, for a fixed DR of 85%, it reduces the number of unnecessary invasive tests from 3.7 to 3.2%. Conclusion:Early evaluation of DV can be introduced to standard DS screening strategies in experienced centers as a first level test to reduce invasive test rate derived from the existing protocols.

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Appropriate biochemical parameters in first-trimester screening for Down syndrome

Cited by 142 publications

References 38 publications

The effect of temporal variation in biochemical markers of trisomy 21 across the first and second trimesters of pregnancy on the estimation of individual patient-specific risks and detection rates for Down's syndrome

The effect of temporal variation in biochemical markers of trisomy 21 across the first and second trimesters of pregnancy on the estimation of individual patient-specific risks and detection rates for Down's syndrome

Combined ultrasound and biochemical screening for Down's Syndrome in the first trimester: a Scottish multicentre study

Impact of Ductus Venosus Assessment in Screening Down Syndrome Protocols: An Improved Strategy in a Fetal Medicine Unit

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