Performance of different methods of estimating risk screening for chromosomal anomalies

In the last 10 years, several studies have been carried out on additional ultrasound markers in the first trimester of pregnancy in order to improve detection rate of fetal numerical chromosome abnormalities (aneuploidy) and to reduce the rate of false-positive diagnosis. The purpose of this study was to evaluate the performance of various recommendations for which amniocentesis was performed followed by FISH testing in the diagnosis of aneuploidy. These evaluations were conducted in order to determine whether ultrasound aspects are associated with fetal aneuploidy and to estimate the risk level of individual markers using probability estimation analysis. The study has been carried out at the Clinical Hospital of Obstetrics and Gynecology "CuzaVodă" Iaşi, at the Laboratory of cytogenetic--prenatal diagnosis, during January 2004-December 2011, on a target group of 1406 pregnant women. As part of this study, 1411 amniocentesis were performed. increased efficiency of screening for fetal aneuploidy in the first trimester of pregnancy is obtained through combined method (maternal age over 35 years, increased nuchal translucency and the presence of double test risk) which has 100% detection rate and a rate false-positive result of 0%. The efficiency of this method is provided also by the relatively high risk (RR = 17.2) and its specificity (Sp = 100%). Making the assessment following the study false positive rate, it appears that a good method of risk assessment for aneuploidy is the combined evaluation of increased nuchal translucency (NT) with maternal age over 35 years (specificity 99.5%, a detection rate of 40% false positive rate of 0.45% and a relative risk of 7.09 for the presence of aneuploidy). The achievement of a correct prenatal diagnosis and the increase of the method efficiency, requires a correct selection of cases with aneuploidy risk assessment, based on the results of ultrasound and biochemical (double test risk) investigations correlated with advanced maternal age or previous presence of aneuploidy of children (Down syndrome, Edwards syndrome, Patau syndrome, Klinefelter syndrome and triplo X).