Comparative Evaluation Between First and Second Trimester Aneuploidy Screening Tests with Amnio Synthesis Results

Screening tests for common aneuploidy, especially trisomies 21, 18, and 13, should be offered to pregnant people of all ages at first and second trimesters. Theses include combined tests (nuchal translucency (NT)+biochemical pregnancy-associated plasma protein-A (PAPP-A), free beta-human chorionic gonadotropin (β-hCG)) and quad test. If the tests are positive based on cut-off value of 1:250, diagnostic tests such as amniocentesis and chorionic villus sampling (CVS) are suggested. The current study aimed to comparatively evaluate the results of these screening tests and amniocentesis.

This practical-basic study was designed to evaluate the accuracy of first and second trimester screening tests with amniocentesis results. A total of 45 subjects were selected from the patients referred for abnormal screening tests toShohadaya-ye-Tajrish hospital in Tehran, Iran, during 2014-2015. The results of tests (combined or quad) were positive based on cut-off value of 1:250. Data was collected through a questionnaire containing such information as age, gravidity, previous aneuploidy births, placenta location, blood group, amniotic fluid color, type of sampling needle, and mode of needle entrance.

The mean age of patients was 33.16 years. There was significant p-value between positive results of amniocentesis and age of the patients. Out of 45 amniocentesis tests, four had abnormal results (two in the first trimester (2/17) and two in the second trimester (2/24)). Also, three items were T21 and the forth was translocation between chromosome 11-22. We had one fetal loss due to amniocentesis procedure.

 Diagnostic tests are suggested for better evaluation of abnormal results. These screening tests have false positive and negative results. We attempted to evaluate the real results with invasive tests. Further research is needed to investigate the accuracy of screening aneuploidy tests.