Maternal serum screening for fetal trisomy 18: a comparison of fixed cutoff and patient-specific risk protocols

Abstract

Overall, the risk-based method is more effective than the fixed-cutoff approach to trisomy 18 screening.

Estimates for the sensitivity and false-positive rates for second trimester serum screening for Down syndrome and trisomy 18 with adjustment for cross-identification and double-positive results

“…Again, the estimates for the performance of trisomy 18 screening applied to a total population also appear to be compatible with earlier estimates (Palomaki et al, 1995;Benn et al, 1999a). All projections for the performance of the screening are based on the assumption that the means, standard deviations, correlation coef®cients of analytes, and prevalence curves are accurate.…”

“…Previous reports have separately evaluated the ef®cacy of second trimester three-or four-analyte screening for Down syndrome Haddow et al, 1992;Wald et al, 1996;Haddow et al, 1998) and three-analyte screening for trisomy 18 (Palomaki et al, 1995;Benn et al, 1999a). Because Down syndrome and trisomy 18 affected pregnancies can share the common characteristics of advanced maternal age, low MS-AFP and low uE3, there should be some additional affected pregnancies identi®ed through one or the other screening protocol that were not speci®cally designed for that particular aneuploidy (`cross-identi®cation').…”

Maternal serum–integrated screening for trisomy 18 using both first‐ and second‐trimester markers

“…Subsequently, an improved method was described (Palomaki et al, 1995), which used individually assigned trisomy 18 risks as a way to identify high-risk pregnancies. The performance of this second-trimester risk-based approach has been confirmed in prospective trials (Benn et al, 1999;Hogge et al, 2001). The current study extends the model to include a combination of both first-and second-trimester serum markers.…”

“…On the basis of this information, screening protocols specifically targeted for trisomy 18 were developed and implemented (Canick et al, 1990;Palomaki et al, 1995). These have been shown to satisfy the performance criteria described above (Benn et al, 1999;Feuchtbaum et al, 2000;Hogge et al, 2001).…”

Prenatal Diagnosis of Down Syndrome

“…In Down syndrome, the MoM of maternal serum PAPP-A is 0.38, decreasing by 60%, and that of free -hCG is 1.83, increasing by around two times. 21 Accordingly, both of the two markers are used in first trimester screening, and with this test, the Down syndrome detection rate is 60-74% and the false positive rate is 5%. 19,20 The detection rate is lower than that of the quad test in the second trimester but similar to that of the triple test.…”