A Study about the Effectiveness of Triple Marker Test as a Screening Test for Chromosomal Aneuploidy

Choi, Y K; Kim, M Y; Han, J Y; Ryu, H M; Yang, J H; Kim, E S; Lee, H B; Han, I S; Ko, M I; Han, H W

Abstract

OBJECTIVE
To evaluate the effectiveness of a screening protocol using a combination of maternal age and three biochemical markers for the antenatal detection of fetal chromosomal aneuploidy
Materials and methods
In our retrospective, 5,308 women who were screened for Down syndrome at second trimester of pregnancy and delivered between March 1994 and February 1996 at Samsung Cheil hospital were studied. Also, 1,378 women were simultaneously studied for screening for Edward syndrome between November 1995 and February 1996. According to maternal age and the concentration of measured maternal serum markers (alpha-fetoprotein, unconjugated E3, hCG), the risk ratio of Down syndrome and Edward syndrome were calculated by alpha-software V. 4.1. The screening positive women were performed amniocentesis for fetal karyotyping after genetic counseling.
RESULTS
The average age was 28 years old. The average of the geatational weeks was 16.3 weeks. The followings are equations of expected median for each maternal serum markers. AFP(ng/ml)=10(0.474+0.0652xGestational week) uE3(nmol/L)=10(-0.852+0.0932xGestational week) hCH(IU/ml)=217,523/[1+Exp(5.62+0.17xGestational week)] Among 5,308 cases, screen positive was in 248 cases(4.7%). But amniocentesis was performed in 126 cases(2.4%). Down syndrome was detected in 7 cases. The difference of the prevalance rate for Down syndrome between younger than 35 years old (1.2/1,000) and older than or equal to 35 years old(6.7/1,000) was statistically significant (P=0.035). However, in screen negative cases, Down syndrome was detected in 2cases. Overall, the detection rate, false positive for Down syndrome were 77.8%, 4.5% respectively and the ratio for OAPR was 1:35. In Edward syndrome, screen positive was in 4 cases(0.3%). Edward syndrome was confirmed in 2 cases by amniocentesis The detection rate, false positive for Edward syndrome were 100%, 0.1 % and the ratio for OAPR was 1:2.
CONCLUSION
The prenatal screening test by the combination of maternal age and the concentration of maternal serum markers was effective to detect Down syndrom and Edward syndrome at second trimester of pregnancy.