Mavrides et al used ultrasonography to screen for aneuploidy in a fetus during the first trimester of a pregnancy. The authors are from St. George's Hospital Medical School in London.
The ductus venosus runs from the left umbilical vein to the inferior vena cava via the liver.
Patient selection: between 11 and 14 weeks gestation
(1) blood flow velocity forms through the ductus venosus using color Doppler measurement
(2) width of the nuchal translucency in mm
Blood flow velocity through the ductus venosus was considered abnormal if it was absent or if it showed reverse flow during atrial contraction.
Nuchal translucency was considered abnormal if the measurement was greater or equal to the 95th percentile for a normal population at that gestational age.
Aneuploidy is suspected if either the blood flow velocity OR nuchal translucence are abnormal.
• An OR function was used rather than AND. The text is ambiguous, but the data in Table 4 on page 1018 favors this interpretation.
• The sensitivity was 94% and specificity 73%.
• The positive predictive value was 44% while the negative predictive value was 98%. Thus the combined test is relatively weak if positive but good for excluding aneuploidy when negative.
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Specialty: Obstetrics & Gynecology, Pedatrics, Genetics