Likelihood ratio of Down syndrome based on the presence of an isolated soft marker (pooled results)

Finding	Sensitivity Down syndrome, percent	False positive rate (ie, marker detected in euploid karyotype), percent	Likelihood ratio if the marker is isolated*
Absent or hypoplastic nasal bone	48.9 to 69.9	1.9 to 4.0	6.58
Aberrant right subclavian artery	17.9 to 47.4	1.0 to 2.1	3.94
Ventriculomegaly^¶	4.2 to 12.9	0.1 to 0.4	3.81
Increased nuchal fold^Δ	20.3 to 32.9	0.5 to 1.9	3.79
Hyperechoic bowel^◊	13.4 to 20.7	0.8 to 1.5	1.65
Pyelectasis^§	11.2 to 17.2	1.4 to 2.0	1.08
Echogenic intracardiac focus	20.9 to 28.2	3.4 to 4.5	0.95
Short humerus	17.1 to 47.9	2.8 to 7.4	0.78
Short femur	19.3 to 38.1	4.7 to 8.8	0.61

Results from meta-analysis of data pooled from 48 studies of low- and high-risk populations. Gestational age at ultrasound 14 to 24 weeks. Most studies involved women at increased risk. The authors concluded that if a systematic ultrasound examination is performed by expert sonologists and all of these markers are absent, the risk of Down syndrome is the mother's a priori risk based on maternal serum screening multiplied by 0.13.

* Derived by multiplying the positive likelihood ratio for the marker by the negative likelihood ratio for each of the other markers EXCEPT short humerus.
¶ Diameter of lateral cerebral ventricle ≥10 mm.
Δ Thickness ≥6 mm.
◊ Echogenicity the same as bone.
§ Anteroposterior diameter 3 to 5 mm.

Data from: Agathokleous M, Chaveeva P, Poon LCY, et al. Meta-analysis of second trimester markers for trisomy 21. Ultrasound Obstet Gynecol 2013; 41:247.

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Likelihood ratio of Down syndrome based on the presence of an isolated soft marker (pooled results)