Screening for chromosomopathies by biochemical markers and their utilization in Croatia

Abstract

The aim is to provide a review of the prenatal screening methods for fetal aneuploidies in Croatia, with special reference to the role of biochemical markers in maternal blood, and to compare the sensitivity and specifi city of various methods of prenatal screening between the fi rst and second trimester of pregnancy. Successful screening, i.e. a satisfactory rate of Down syndrome detection with minimal rate of false-positive screening results, is achieved by choosing appropriate type and number of markers, along with overall screening quality control and quality assurance. Target criterion for screening in the general population of pregnant women is >75% detection with no more than 5% of false-positive results. The following models of prenatal screening by biochemical assays are used in Croatia: in the fi rst trimester, a combination of nuchal thickness and biochemical screening with free βhCG and PAPP-A for common risk calculation (combined screening), with chorionic villus karyotyping as a confi rmation diagnostic method; and in the second trimester, triple (uE3 + total βhCG + AFP) or double (free βhCG + AFP) biochemical screening, with amniotic fl uid cell karyotyping as a confi rmation diagnostic method. Optimal models of successful screening of pregnant women before an invasive procedure, which meet the above mentioned criteria, are combined ultrasonographic and biochemical screening in the fi rst trimester and triple (uE3 + total βhCG + AFP) biochemical screening in the second trimester of pregnancy.