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Combined Sonographic and Biochemical Markers for Down Syndrome Screening
Author(s) -
Pinette Michael G.,
Egan James F.X.,
Wax Joseph R.,
Blackstone Jacquelyn,
Cartin Angelina,
Benn Peter A.
Publication year - 2003
Publication title -
journal of ultrasound in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 91
eISSN - 1550-9613
pISSN - 0278-4297
DOI - 10.7863/jum.2003.22.11.1185
Subject(s) - medicine , cutoff , false positive rate , obstetrics , population , fetus , prenatal diagnosis , pregnancy , gynecology , statistics , physics , mathematics , environmental health , quantum mechanics , biology , genetics
Objective . To evaluate the efficacy of fetal nuchal fold thickness and proximal long bone biometric measurements in modifying Down syndrome serum screening risk in a population of women referred for second‐trimester sonography. Methods . Sonographic biometric measurements and biochemical markers were combined retrospectively for 2533 women with known pregnancy outcomes. Four different screening methods were compared: (1) advanced maternal age; (2) biochemical serum screening markers; (3) modification of serum screening risks on the basis of categorical cutoffs for nuchal fold and femur and humerus length; and (4) a combined approach in which the sonographic measurements were treated as multiples of the medians and entered, together with the serum screening results, into a multivariable algorithm. The efficacy was compared at second‐trimester risk cutoffs of 1:270 and 1:100. Results . Down syndrome was present in 30 of the 2533 pregnancies (1 in 84). With the use of the 1:270 cutoff, biochemical screening had 93% sensitivity and a 40% false‐positive rate. With application of the categorical method of fixed cutoffs to incorporate fetal biometry, the false‐positive rate was reduced to 33% with no loss of sensitivity. The combined model had 83% sensitivity and a 19% false‐positive rate. The combined method had the highest positive predictive value (1 in 20). Similar gains in efficacy could be shown with the 1:100 cutoff. Conclusions . For this high‐risk group, the multivariate model that combines serum screening and sonography can result in a substantial reduction in the number of amniocenteses. Although the addition of the sonographic biometric measurements resulted in some Down syndrome cases being missed, the net effect was a large improvement in the overall positive predictive value of the screening.