Erratum. Letter to the Editor: Inhibin-A in Down's syndrome pregnancies: revised estimate of standard deviation

Wald, Nicholas; Densem, J. W.; George, Lynne M.; Muttukrishna, S; Knight, P. G.; Watt, Hilary; Hacksaw, A.; Morris, Joan K.

doi:10.1002/(sici)1097-0223(199703)17:3<285::aid-pd71>3.0.co;2-a

Cited by 37 publications

(26 citation statements)

References 3 publications

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“…These population parameters were computed using regression analysis of the data between the fifth and 95th centiles. 30 Pairwise correlation coeYcients were then generated (after appropriate transformations) between the dimeric inhibin-A measurements and other second trimester serum markers that had been reported previously. 4 31 These parameters and correlations were then used to model Down's syndrome risk in a general pregnancy population 32 to predict expected screening performance.…”

Section: Discussionmentioning

confidence: 99%

Clinical validation of a new dimeric inhibin-A assay suitable for second trimester Down's syndrome screening

Knight

Palomaki²,

Neveux³

et al. 2001

J Med Screen

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Objective-To compare the Down's syndrome screening performance of a simplified dimeric inhibin-A assay (Diagnostic Systems Laboratories (DSL)) with an assay whose clinical utility has been established (Serotec). Setting-A case control set consisting of 51 Down's syndrome and 245 matched unaVected pregnancies collected as part of an earlier multicentre cohort study. Methods-Sera were assayed for dimeric inhibin-A using the DSL assay and Serotec reference assay. Data analysis included a method comparison of mass values, fit of data to a logarithmic Gaussian distribution, and determination of detection and false positive rates. In addition, 234 fresh sera were assayed using the simplified method. Results-The two assays showed a high correlation (r =0.93) but average concentrations of the DSL assay were 48% higher. However, the diVerences were basically proportional over the range of values important for screening. The detection rate was essentially equivalent for the DSL assay whether analysed univariately or in combination with other markers (for example, 79% v 75% at a 5% false positive rate for the DSL and Serotec assays for the combination of fetoprotein, unconjugated oestriol, human chorionic gonadotrophin, and dimeric inhibin-A, respectively). The 234 dimeric inhibin-A values measured on fresh sera fitted a logarithm Gaussian distribution for the DSL assay, as indicated by the fit to a probability plot. Conclusions-TheDown's syndrome screening performance of a simplified dimeric inhibin-A immunoassay was equivalent to a more labour intensive established dimeric inhibin-A assay. (J Med Screen 2001;8:2-7)

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Section: Discussionmentioning

confidence: 99%

Clinical validation of a new dimeric inhibin-A assay suitable for second trimester Down's syndrome screening

Knight

Palomaki²,

Neveux³

et al. 2001

J Med Screen

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“…The mean AFP levels in aVected pregnancies were obtained from Wald et al 10 Previously, it was estimated that 2% of women with unaVected pregnancies would have an AFP of > 2.5 MoM if gestational age is estimated by dates; now it is only 0.8%. Table 3 shows the screening performance for Down's syndrome for the double test (AFP and free human chorionic gonadotrophin (free hCG)), the triple test (AFP, total hCG and uE 3 ) and the quadruple test (triple test plus inhibin A) using the previously published means, standard deviations and correlation coeYcients, [3][4][5] and the present ones. Using gestational age based on scan at a 5% false positive rate, the present estimate of the detection rate is about 2 to 5 percentage points greater than that previously published.…”

Section: Methodsmentioning

confidence: 99%

“…These data were based on estimating gestational age from the first day of the last menstrual period, with and without maternal weight correction, and on a biparietal diameter scan measurement (again, with and without weight correction) using data from 970 white women screened at the Homerton Hospital, London, from 1989 to 1990. [3][4][5] Estimates for anencephaly and open spina bifida were based on data from the UK Collaborative AFP Study (177 cases), 6 7 and those for Down's syndrome from a series from Oxford (77 cases).3-5 They were also adjusted to take account of the method of estimating gestational age (dates or scan) and maternal weight.Four hundred and seventy serum samples from the dataset of 970 white women with unaVected pregnancies were randomly retrieved from storage (−40°C) and thawed. AFP was measured over a period of about five weeks using an auto DELFIA AFP fluorometric immunoassay kit (DELFIA, Wallac, Finland), as in routine practice.…”

mentioning

confidence: 99%

Assay precision of serum α fetoprotein in antenatal screening for neural tube defects and Down's syndrome

2000

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Objectives-To assess the impact of current serum fetoprotein (AFP) assays on the performance of screening for open neural tube defects and Down's syndrome. Methods-Maternal serum samples, collected between weeks 15 and 22 from 470 singleton pregnancies without neural tube defects or Down's syndrome, were assayed for AFP using an automated fluorometric immunoassay. The samples had been assayed for AFP using an in house radioimmunoassay with a lower precision ten years before. The variance of AFP using the radioimmunoassay was compared with that using the current fluorometric assay and then used to estimate the detection rates and false positive rates for neural tube defect and Down's syndrome screening. Results-Current serum AFP assays are more precise. Using a cut oV level of 2.5 multiples of the median, the false positive rate in screening for anencephaly and open spina bifida was 0.8% with the new assay compared with 2% using the previous assay. When screening for Down's syndrome, the false positive rate is reduced by about one percentage point without loss of detection. Recently, it has become apparent when using serum AFP measurement as a screening test for open neural tube defects, that the observed positive rate (that is the proportion of women screened with raised AFP levels) is lower than that expected on the basis of serum AFP distribution parameters estimated about 10 years ago. Conclusion-ImprovementsA reduction in the serum AFP screen positive rate is not surprising. The eYcacy of screening using AFP measurement is determined by the distribution of serum AFP in aVected and unaVected pregnancies-the less overlap in the distributions, the better the test. A reduced overlap is reflected in a reduced standard deviation, and this will probably arise due to more precise serum AFP measurement. We examine the eVect of the improvement in precision on the standard deviation of AFP at 15 to 22 weeks of pregnancy, and we estimate the resulting improvement in the performance of antenatal screening for open neural tube defects and Down's syndrome. MethodsEstimates of the standard deviation of maternal serum AFP (and the correlation between AFP and the other serum markers) in unaffected pregnancies at any given gestational age from 15 to 22 weeks of gestation have been published. These data were based on estimating gestational age from the first day of the last menstrual period, with and without maternal weight correction, and on a biparietal diameter scan measurement (again, with and without weight correction) using data from 970 white women screened at the Homerton Hospital, London, from 1989 to 1990. [3][4][5] Estimates for anencephaly and open spina bifida were based on data from the UK Collaborative AFP Study (177 cases), 6 7 and those for Down's syndrome from a series from Oxford (77 cases).3-5 They were also adjusted to take account of the method of estimating gestational age (dates or scan) and maternal weight.Four hundred and seventy serum samples from the dataset of 970 white women with unaVected...

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“…These markers include ␣-fetoprotein (AFP), unconjugated estriol (uE3), human chorionic gonadotropin (hCG), and dimeric inhibin-A (DIA). [1][2][3][4][5][6][7] Unless otherwise noted, measurements of the free ␤ subunit of hCG can be used interchangeably with hCG measurements. 8…”

Section: Ds3 Second Trimester Maternal Serum Screening For Down Syndromementioning

confidence: 99%

Technical standards and guidelines: Prenatal screening for Down syndrome: This new section on “Prenatal Screening for Down Syndrome,” together with the new section on “Prenatal Screening for Open Neural Tube Defects,” replaces the previous Section H of the American College of Medical Genetics Standards and Guidelines for Clinical Genetics Laboratories

Palomaki

Bradley²,

McDowell

2005

Genetics in Medicine

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21) is one of the most common genetic causes of moderate to severe mental retardation. Virtually all individuals with Down syndrome are hypotonic and have minor dysmorphic features, which can include up-slanting palpebral fissures, epicanthal folds, flat nasal bridge, Brushfield spots of the iris, shortened fifth finger, and transverse palmar crease. Congenital heart disease is present in 40%, and 5% have gastrointestinal anomalies such as duodenal atresia or Hirschsprung disease. The incidence of childhood leukemia is increased up to 20 times over that of the general population. Adults with Down syndrome experience neuronal degeneration identical to that present in Alzheimer's disease. Down syndrome individuals without congenital heart disease can live beyond 60 years of age.DS2.3 ETIOLOGY. Down syndrome is caused by the presence of an extra copy of chromosome 21, either as a free chromosome, a Robertsonian translocation, or a reciprocal translocation involving chromosome 21. Approximately 95% of cases result from sporadic nondisjunction during parental meiosis. The nondisjunction is maternal in 95% of cases, and 77% of the maternal nondisjunction occurs during meiosis I. The risk of having a child with Down syndrome increases with advancing maternal age. Down syndrome can be inherited when one parent carries a translocation involving chromosome 21. If a parent carries a Robertsonian translocation, the risk to the offspring is dependent on the sex of the carrier parent. DS2.4 LABORATORY DIRECTOR.Although the prenatal screening laboratory utilizes clinical chemistry methods such as enzyme immunoassays, its function differs, because the results require a unique kind of interpretation. This interpretation puts the results of the test into the appropriate context of a priori risks as determined by maternal age, gestational age, and family history. The laboratory director is often called upon to provide consultation regarding these risks and options for further action. To address these unique requirements, the laboratory director should meet the standards set out in Section B3 of the ACMG guidelines. When prenatal screening for Down syndrome is performed in a clinical chemistry laboratory in which the director does not meet these standards, the laboratory should have a demonstrated relationship with an individual Women and Infants Hospital, Providence, Rhode Island. From the G.E. Palomaki's present address is

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Erratum. Letter to the Editor: Inhibin-A in Down's syndrome pregnancies: revised estimate of standard deviation

Cited by 37 publications

References 3 publications

Clinical validation of a new dimeric inhibin-A assay suitable for second trimester Down's syndrome screening

Clinical validation of a new dimeric inhibin-A assay suitable for second trimester Down's syndrome screening

Assay precision of serum α fetoprotein in antenatal screening for neural tube defects and Down's syndrome

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