Genetic sonogram scoring index: accuracy and clinical utility.

Area of Science:

• Prenatal diagnosis
• Medical imaging
• Genetics

Background:

• Down syndrome (trisomy 21) is a common chromosomal abnormality.
• Accurate prenatal detection is crucial for genetic counseling and management.
• The genetic sonogram scoring index (GSSI) is a tool to assess fetal aneuploidy risk.

Purpose of the Study:

• To evaluate the accuracy of the GSSI in detecting Down syndrome in a high-risk population.
• To compare the GSSI's performance with and without maternal age consideration.
• To determine the optimal threshold for recommending karyotype testing.

Main Methods:

• Prospective evaluation of 1118 fetuses from women referred for genetic sonogram.
• Application of the GSSI to assign a risk score to each fetus.
• Karyotype determination for fetuses with a GSSI of 1 or greater.
• Analysis of detection rates and false positive rates for Down syndrome.

Main Results:

• A GSSI of 1 or greater identified 62.5% of Down syndrome fetuses (5/8), with a 14.6% false positive rate.
• Including maternal age ≥40 increased Down syndrome detection to 75% (6/8), with a 26.3% false positive rate.
• Three Down syndrome cases were missed by the GSSI alone, with one case missed when maternal age was considered.

Conclusions:

• The GSSI is a valuable tool for identifying fetuses with Down syndrome, detecting approximately 75% of affected cases.
• Integrating maternal age with the GSSI enhances detection rates and optimizes the recommendation for invasive procedures like amniocentesis.
• The GSSI, particularly when combined with maternal age, aids in risk stratification for Down syndrome in high-risk pregnancies.