Journal of Ultrasound in Medicine

Growing evidence is showing the usefulness of lung ultrasound in patients with the 2019 new coronavirus disease (COVID‐19). Severe acute respiratory syndrome coronavirus 2 has now spread in almost every country in the world. In this study, we share our experience and propose a standardized approach to optimize the use of lung ultrasound in patients with COVID‐19. We focus on equipment, procedure, classification, and data sharing.

To determine whether sonographic "markers" are associated with fetal Down syndrome during the second trimester and to estimate the degree of risk of individual markers using likelihood ratios.

Second‐trimester (14‐20 weeks) sonographic findings in 186 fetuses with trisomy 21 were compared with a control group of 8728 consecutive control fetuses. Six markers were evaluated: nuchal thickening, hyperechoic bowel, shortened femur, shortened humerus, echogenic intracardiac focus, and renal pyelectasis.

Major or structural abnormalities were observed in 31 fetuses with trisomy 21 (16.7%) and 53 control fetuses (0.6%) (P< .001). Some type of sonographic finding (major abnormality, minor marker, or both) was observed in 68.8% of fetuses with trisomy 21 compared with 13.6% of control fetuses (P < .001). An isolated minor or "soft" marker was the only sonographic finding in 42 (22.6%) of 186 fetuses with trisomy 21 compared with 987 (11.3%) of 8728 control fetuses (P < .001). Nuchal thickening (P < .001; likelihood ratio, 11) and hyperechoic bowel (P < .001; likelihood ratio, 6.7) showed the strongest association with trisomy 21 as isolated markers, followed by shortened humerus (likelihood ratio, 5.1), echogenic intracardiac focus (likelihood ratio, 1.8), shortened femur (likelihood ratio, 1.5), and pyelectasis (likelihood ratio, 1.5). Echogenic intracardiac focus was the single most common isolated marker in both affected fetuses (7.1%) and control fetuses (3.9%) but carried a low risk (P= .046; likelihood ratio, 1.8).

A single soft marker is commonly encountered during the second trimester among fetuses with trisomy 21. The risk of fetal Down syndrome, reflected by likelihood ratios, was determined for 6 individual markers. This information can be combined with the a priori risk to estimate the individual patient risk for fetal Down syndrome.

Objective. To determine the risk of Down syndrome in fetuses with sonographic markers using the Bayes theorem and likelihood ratios. Methods. We prospectively evaluated the midtrimester sonographic features of fetuses with Down syndrome and compared them with euploid fetuses. Patients were referred for an increased risk of aneuploidy and evaluated for the presence of structural defects, a nuchal fold, short long bones, pyelectasis, an echogenic intracardiac focus, and hyperechoic bowel. All fetuses underwent amniocentesis at the time of sonographic assessment. The sensitivity, specificity, and likelihood ratios for markers were calculated both as nonisolated and isolated findings. Results. There were 164 fetuses with Down syndrome and 656 euploid fetuses. The presence of any marker resulted in sensitivity for the detection of Down syndrome of 80.5% with a false‐positive rate of 12.4%. The absence of any markers conferred a likelihood ratio of 0.2, decreasing the risk of Down syndrome by 80%. As an isolated marker, the nuchal fold had an “infinite” likelihood ratio for Down syndrome; a short humerus had a likelihood ratio of 5.8, whereas structural anomalies had a likelihood ratio of 3.3. Other isolated markers had low likelihood ratios because of the higher prevalence in the unaffected population. The likelihood ratios for the presence of 1, 2, and 3 of any of the markers were 1.9, 6.2, and 80, respectively. Conclusions. Although an isolated marker with a low likelihood ratio may not increase a patient's risk of Down syndrome, the presence of such a marker precludes reducing the risk of aneuploidy. Clusters of markers appear to confer a higher risk.