Model-predicted performance of second-trimester Down syndrome screening with sonographic prenasal thickness

Area of Science:

• Prenatal diagnostics
• Medical imaging
• Genetics

Background:

• Second-trimester screening is crucial for detecting fetal abnormalities.
• Prenatal thickness (PT) is a sonographic marker used in fetal assessments.
• Accurate estimation of Down syndrome detection and false-positive rates is essential for effective screening.

Purpose of the Study:

• To estimate Down syndrome detection and false-positive rates using second-trimester sonographic prenasal thickness (PT) measurement.
• To evaluate the effectiveness of PT alone and in combination with other markers for Down syndrome screening.

Main Methods:

• Multivariate log Gaussian modeling was employed for data analysis.
• Prenatal thickness (PT) distribution parameters were derived from 105 Down syndrome and 1385 unaffected pregnancies.
• Data from new and previously published series were combined for robust parameter estimation.

Main Results:

• A log Gaussian model accurately fitted PT values in both Down syndrome and unaffected pregnancies.
• Prenatal thickness (PT) alone predicted detection rates of 35%, 51%, and 60% for 1%, 3%, and 5% false-positive rates, respectively.
• Combining PT with serum markers or additional sonographic markers (nasal bone length, nuchal skin fold) significantly improved detection rates.

Conclusions:

• Second-trimester screening incorporating sonographic PT and serum markers is predicted to achieve high Down syndrome detection rates.
• The addition of further sonographic markers can lead to performance comparable to first-trimester screening protocols.