Objectives: The aim of the study was to compare effects of addition of two methods of ductus venosus (DV) flow assessment: qualitative - the assessment of shape of the A-wave (positive or negative), and quantitative - based on the pulsatility index for veins (DVPI) to the basic screening for trisomy 21 at 11 to 13 + 6 weeks of pregnancy.
Material and methods: The ultrasound examination was performed in 8230 fetuses in singleton pregnancies at 11- -13 + 6 wks, as a part of a routine screening for chromosomal defects. In DV A-wave was assessed and DVPI was calculated. After the scan blood sample was taken for first trimester biochemistry (BC). Risk for chromosomal defects was calculated and high-risk patients were offered an invasive test for karyotyping.
Results: Basic screening with following combination of markers: MA, NT and BC provided lowest detection rate (DR) 87.50% for FPR = 6.94%. After adding qualitative DV A-wave assessment DR increased to 88.75% for FPR = 5.65%. The best DR = 93.75% for FPR = 5.55% was achieved when quantitative DVPI was added. The application of the Receiver Operating Curves curve confirmed validity of the addition of DV flow assessment to the screening model. The highest diagnostic power of the test was achieved when DVPI was added, with the ROC AUC of 0.974.
Conclusions: The assessment of DV flow performed at 11-13 + 6 weeks increases DR for trisomy 21 and reduces FPR. The screening model based on the quantitative DV flow analysis (DVPI) gives better results compared to the qualitative flow assessment.
Keywords: 11 to 13 + 6 weeks scan; ductus venosus; screening for chromosomal defects; trisomy 21.