Abstract
SummaryBackgroundGenetic screening for chromosomopathy is performed in the first trimester of pregnancy by determining fetal nuchal translucency (NT), and the pregnancy associated plasma protein-A (PAPP-A) and free human chorionic gonadotropin (free-beta HCG) biomarkers in maternal serum.MethodsWe tested the sensitivity, specificity, positive and negative expected values of each marker with the aim of setting a model for prenatal screening readings. Statistical data treatment has been performed on a sample of 340 pregnant women with positive results of prenatal screening.ResultsSensitivity of PAPP-A was 0.6250 (probability 62.50%), free beta HCG 0.5893 (58.93%), NT 0.1785 (17.85%). Specificity of PAPP-A was 0.5106 (probability 51.06%), free beta HCG 0.5246 (52.46%), NT 0.9718 (97.18%). Positive expected value of PAPP-A was 0.2011 (probability 20.11%), free beta HCG 0.1964 (19.64%), NT 0.556 (55.56%). Negative expected value of PAPP-A was 0.8735 (probability 87.35%), free beta HCG 0.8662 (86.62%), NT 0.8571 (85.71%). The NT marker has a significantly higher specificity, which means that its normal value will significantly reduce the final risk of trisomy 21. The sensitivity of NT is much lower than that of biochemical markers, which means that a pathological value of NT does not have a significant influence on the final risk, i.e. the significantly higher sensitivity of biochemical markers will reduce the final risk of trisomy 21.ConclusionsThe analyses stress the importance of using a software which has the possibility to separate the level of a biochemical risk by correlating PAPP-A and free beta HCG and, by adding the NT marker, calculate the level of a final risk of Down syndrome.
Highlights
Prenatal screening for Down’s syndrome is done in the first trimester of pregnancy between 11 and 14 weeks by the ultrasound measurement of nuchal translucency (NT-neck crease) and the determination of fetal maternal serum biomarkers: pregnancy-associated plasma protein-A (PAPP-A) and free beta human chorionic gonadotropin
The analyses stress the importance of using a software which has the possibility to separate the level of a biochemical risk by correlating PAPP-A and free beta HCG and, by adding the NT marker, calculate the level of a final risk of Down syndrome
There is no significant association between fetal NT and maternal serum free beta hCG and PAPP-A in either trisomy 21 or euploid pregnancies [6]
Summary
Prenatal screening for Down’s syndrome is done in the first trimester of pregnancy between 11 and 14 weeks by the ultrasound measurement of nuchal translucency (NT-neck crease) and the determination of fetal maternal serum biomarkers: pregnancy-associated plasma protein-A (PAPP-A) and free beta human chorionic gonadotropin (free beta-hCG). The risk of Down’s syndrome is determined i.e. calculated by a combination of software processing of the maternal characteristics, biochemical and sonographic markers. It has been estimated that the false-positive rate in genetic screening is about 5%, which has resulted in an increased number of invasive diagnostic procedures of prenatal karyotyping in risk free pregnant women with respect to age [7]. The performance of different screening methods for trisomy 21 with a combination of maternal age, sonographic and biochemical markers has been tested. Specificity, positive and negative expected values of each marker with the goal of setting a model for prenatal screening readings and interpretation of pathological values
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