Study On A Disintegrin And Metalloprotease12 In Prenatal Diagnosis For Down Syndrome

Chapter One Assessment of the value of maternal serum screening of Down syndrome for women with advanced maternal age1 BackgroundDown syndrome (DS) is the most common cause of severe mental retardation in children. The rate of Down syndrome for live births is between 1/600～1/800. It is the result of trisomy of chromosome 21 which is usually a random event though it is commoner in older mothers. Such children will be a heavy financial and emotional burden for the family and society because of lacking effective treatment measures. Down syndrome can be diagnosed by chorionic villus sampling (CVS) and amniocentesis followed by karyotyping. Because of the risks associated with these invasive procedures, they can only be offered to a high-risk pregnant women. Non-invasive biochemical screening for Down syndrome is well established in the second trimester of pregnancy. Second-trimester screening traditionally consists of some combination of maternal serum analysis and maternal age. Screening programmes in Mainland of China involving the measurement of maternal serum alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG) with or without unconjugated estriol (uE3)(double/triple screening test). Taking into account of the actual situation of economy & technology and the cost-effectiveness of program, We used double-screening (AFP+free P-hCG) test in our prenatal diagnosis center between the 14 to 20 weeks of gestation. Diagnostic amniocentesis was performed as routain in women over 35 years and in women with a previous affected child, but recently, some scholars proposed such opinion that amniocentesis may be offered on a selective rather than routine basis in women w ith advanced maternal age.We had evaluated the double-screening programs in the second trimester, assessed the value of maternal serum screening (MSS) of Down syndrome for women with advanced maternal age (AMA, over 35 years) and tried to lessen the rate of amniocentesis.2 Objectives2.1 To evaluated the double-screening programs in the second trimester in our prenatal diagnosis center for Down syndrome.2.2 To assess the value of maternal serum screening (MSS) of Down syndrome for women with advanced maternal age (AMA, over 35 years)in the second trimester.3 MethodsFrom June 2004 to December 2009, pregnant women between 15+0 and 20-6 weeks of gestation, who received prenatal screening for Down syndrome in the Women’s Hospital, College of Medicine, Zhejiang University were retrospectively analyzed. Levels of freeβ-hCG and AFP were measured by commercial time-resolved fluoroimmunoassay. Statistical analysis was performed using SPSS 16.0 software to evaluate the relationship between each serum marker and weight, gestational age, and the correlations between markers were analyzed too. Down syndrome risk of each pregnancy was calculated by computer software. Screening positive pregnant women were offered genetic counseling and the option of amniocentesis and cordocentesis. The detection rate (DR), false positive rate (FPR), positive predictive value were calculated.4 ResultsIn our study, there were 94405 pregnant women were tested, at a cut-off value of 1 in 270,3316 cases have positive results, in which 156 positive results belong to 1886 cases of women with advanced maternal age (AMA, over 35 years). The total positive MSS rate of Down is 3.5%,98 neonates were diagnosed as Down syndrome by amniocentesis, only 3 cases of Down syndrome was AMA. Other 17 cases of Down syndrome were confirmed as Down syndrome after birth (defined as fals negative cases). The detection rate (DR) was 85.21%(98/115), false positive rate (FPR) was 3.41%(3218/94307), and the positive predictive value (PPV) was 2.96%(98/3316). The detection rate and positive predictive value of AMA were similar with the younger. However, the false positive rate was significantly higher (8.13% vs. 3.32%) of AMA than the pregnancies younger than 35. There is no trisomy 21 in AMA group with negative results of MSS.5 ConclusionsAll pregnant women should be informed the screening test dosen’t equal to diagnosis because of the false negative result. The screening test is effective for women with advanced maternal age. Because amniocentesis is of invaive, there is no necessar y to ask all AMA pregnant women to have amniocentesis and chromosome analysis for safety.6 InovationsThe detection rate of double screening test for Down syndrome in second trimester is relatively low, all pregnant women should be informed the screening test dosen’t equal to diagnosis because of the false negative result. For women with advanced maternal age, serum screening is still an effective method to reduce the the proportion of invasive prenatal diagnosis and lower the risks of fetal loss. Chapter Two ADAM12 is an Effective Marker in the Second Trimester of Pregnancy for Prenatal Screening of Down Syndrome1 BackgroundPrenatal screening developed rapidly in rencent years. Biochemical screening for Down syndrome (DS) is well established, and the serum marker involves maternal serum alpha-fetoprotein (AFP), unconjugated estriol (uE3), and human chorionic gonadotropin (hCG) inhibin-A (INH-A), and so on. A Disintegrin and metalloproteinase 12 (ADAM 12) is discovered recently, which is considered increasing the detection rate of DS screening significantly. Many studies have suggested that ADAM 12 is an useful serum marker for prenatal screening of Down syndrome during the first trimester, fewer scholars studied the effection of ADM 12 in second trimester for prenatal screening of Down syndrome. Taking into account of the actual situation of economy & technology and the cost-effectiveness of program, double screening(AFP+ freeβ-Hcg) in second trimester is the widely used screening mode in the mainland of China. First trimester prenatal screening has not been accepted in our country. So using ADAM 12 in the second trimester for prenatal screening of Down syndrome is more fit for China’s national conditions.2 ObjectivesThe study was designed to explore the changing trends of the levels of maternal serum ADAM12 used in second-trimester Down syndrome screening. To estimate the utility of maternal serum ADAM12 as a second trimester Down syndrome serum marker. 3 MethodsSamples from a total of 46 Down syndrome pregnancies(including 24 false negative cases) and 184 unaffected singleton pregnancies matched for gestational age and maternal weight were retrieved from storage and measured for ADAM 12 by time-resolved fluoroimmunoassay; 35 false positive pregnancies were included among the controls to assess reductions in false positive rates by inclusion of ADAM 12 in the risk calculation of an algorithm that utilized AFP and hCG (double screening).4 ResultsADAM 12 was measured and expressed as multiple of the gestation-specific median (MoM) and corrected for maternal weight. The median ADAM 12 level in the affected pregnancies was 1.26 MoM compared with 1.0 MoM in the unaffected control pregnancies (p<0.05). In unaffected pregnancies, there was a significant correlation between ADAM 12 and AFP (r=0.314) but not hCG (r=0.018). Statistical modeling predicted that ADAM 12 as a second serum marker could increase the detection rate from 48% to 85%, while reducing the false-negative and false-positive rates.5 ConclusionsADAM 12 can be used as an effective second trimester serum marker for prenatal screen of Down syndrome.6 InnovationsWe used ADAM 12 in prenatal screening of Down syndrome in the second trimester, studied the distribution of ADAM 12 in the Chinese population. We evaluated the function of ADAM 12 in improving the detection rate and reducing the false positive rate. There were few reports about using AD AM12 in false negative cases. Our results has been published in SCI journal. Chapter Three The correlations between ADAM12 and other serum markers in prennatal screening of Down Synrome during the first and second trimesters1 BackgroundPrenatal screening for Down syndrome was performed by risk calculation based on biochemical and biometric parameters. The serum marker involves maternal serum alpha-fetoprotein (AFP), unconjugated estriol (uE3), pregnancy-associated plasma protein A (PAPP-A), the freeβ-subunit of human chorionic gonadotrophin (freeβ-hCG) and human chorionic gonadotropin (hCG), inhibin-A (INH-A), and so on. In China’s mainland, double-screening was the main method in second trimester for risk calculation, first trimester prenatal screening has not yet carried out widespread in China, but it is undoubtedly the tendency of the future clinical work with prenatal screening. A Disintegrin and metalloproteinase 12 (ADAM 12) is a recently discovered new serum marker, which is considered increasing the detection rate of Down syndrome screening significantly. Study the correlation between ADAM 12 and other serum markers in the first and second trimester for prenatal screening of Down syndrome to optimize the existing prenatal screening programs.2 ObjectivesTo explore maternal serum freeβ-hCG, PAPP-A, AFP and ADAM 12 levels in the first and second trimester in local Chinese population, in order to evaluate whether ADAM 12 can be an independent marker for prenatal screening of Down synrome. 3 MethodsFrom August 2005 to October 2009, maternal serum samples were collected from women with singleton pregnancy younger than 35 years,339 from first trimester, 1104 from sceond trimester including 22 Down syndrome pregnancies in the Women’s Hospital, College of Medicine, Zhejiang University. Levels of freeβ-hCG, PAPP-A, AFP and ADAM 12 were measured by commercial time-resolved fluoroimmunoassay. Statistical analysis was performed using SPSS 16.0 software to evaluate the relationship between each serum marker and weight, gestational age, and the correlations between markers were analyzed too.4 ResultsThere was no significant differences were found between the maternal ages and weights in each gestational week, and no correlations were found between the maternal weights and gestational weeks either (P>0.01 for all). The ADAM12 levels increased with gestational age and correlated significantly with PAPP-A during the first trimester, with AFP during the second trimester, no significant correlation were found with freeβ-hCG levels. In the second trimester Down syndrome pregnancies, the median ADAM12 MoM was approximately 1.2 times increased compared to normal pregnancies.5 ConclusionThe maternal serum ADAM 12 concentration was increased with the gestational age increased in local Chinese population and correlated significantly both with PAPP-A and AFP levels. No correlation was found between the levels of ADAM12 and freeβ-hCG. ADAM12 is an effective serum marker for prenatal diagnosis of Down syndrom during the second trimester. ADAM12 may not be an independent marker, but it might be used as an additional marker to strengthen the influence of other markers in prenatal screening for Down syndrome during the first and second trimesters.6 InnovationsOur study revealed the changing trend of maternal serum PAPP-A, freeβ-hCG, AFP and ADAM 12 during the first and second trimester in local Chinese population. We studied the correlation between ADAM 12 and other serum markers and we suggest that ADAM 12 should not be an entirely independent marker for Down syndrome screening. Chapter Four Second trimester maternal serum ADAM12 level in normal twin pregnancies1 BackgroundOver the past decade, twin pregnancies are becoming more frequent due to the wide use of various ovulation induction drugs and assisted reproduction technology and advanced maternal age. The incidence of having at least one Down Syndrome-affected fetus in twin pregnancies was higher than that of singleton pregnancies, thus it is important to carry out prenatal screening for twin pregnancies. However, the value of maternal serum screening in twin pregnancies is still controversial. Many studies have shown ADAM 12 is an effective maternal serum marker sensitive and specific for prenatal screening of Down syndrome in singleton pregnancies during the first and second trimester, there is no report about using ADAM 12 in prenatal screening of Down syndrome in twins during the second trimester.Double screening in second trimester is widely used in mainland of China, establishing reference values of ADAM 12 and trying to apply it for prenatal screening of the twin pregnancy during the second trimester has higher clinical value.2 Objectives2.1 To explore the changing trends of maternal serum AD AM12 levels in the second trimester for twin pregnancies.2.2 Comparing the differences of ADAM12 levels between the twins and the singleton controls to see whether ADAM 12 can be used for Down syndrome screening in the second trimester for twins. 3 MethodsThe concentrations of ADAM12 of normal twins and singleton controls at gestational weeks 15+0 to 19+6 were measured. The Wilcoxon rank sum test was performed to compare the differences of ADAM12 between twins and singletons at different gestational ages. Correlations were determined using Pearson’s correlation coefficient for ADAM12 and other markers. Statistically significant differences were considered when p<0.05.4 ResultsThe study group comprised 306 twin pregnancies,31 twins following various forms of ART. In this study,939 singleton pregnancies women in the 15 to 19 weeks of gestation were enrolled,932 women with normal singleton pregnancies were selected as model controls, other 7 Down syndrome affected pregnancies including 2 false-negative cases diagnosed after birth were all excluded. In twin pregnancies, ADAM12 concentrations ranged from 465.69 to 1616.72 ng/ml. The overall median ADAM12 MoM in twins was 1.33 MoM while 1.0 MoM in singleton, in twin pregnancies, no significant correlation were present between the ADAM12 and freeβ-hCG (r=-0.003, p=0.964) and AFP (r= 0.54, p=0.343).5 ConclusionsThe median ADAM12 MoM in euploid twins is significantly increased comparing with singletons, ADAM12 may be an useful marker to prenatal screening of twins during the second trimester.6 InnovationsWe established the distribution of maternal serum ADAM12 for twin pregnancies during the second trimester. Study for ADAM12 in Chinese twin pregnancies will help to establish specific second trimester Down syndrome screening model for Chinese twin-prenatal care.