Practitioner-specific medians for nuchal translucency to improve first-trimester screening performance

Area of Science:

• Prenatal screening
• Maternal-fetal medicine
• Genetics

Background:

• Nuchal translucency (NT) measurements are crucial for first-trimester risk assessment of chromosomal abnormalities.
• Converting NT measurements to multiples of the median (MoM) is standard practice.
• Debate exists on using practitioner-specific versus population-based medians for MoM calculation, impacting bias correction.

Purpose of the Study:

• To evaluate the impact of using practitioner-specific medians versus population-based medians on prenatal screening performance.
• To assess the effect on detection rates for Down syndrome and Trisomy 18.
• To determine if using population-based medians would lead to missed diagnoses.

Main Methods:

• Retrospective analysis of 55,286 first-trimester specimens from the California Prenatal Screening Program.
• Recalculation of risk assessments using population-based medians for cases initially assessed with practitioner-specific medians.
• Comparison of positive rates and examination of recalculated risks for confirmed chromosomal abnormalities.

Main Results:

• The majority of practitioners would have lower NT MoM values if population-based medians were used.
• Analysis indicated that 14 positively diagnosed cases would have been missed if population-based medians were applied.
• Screening performance was significantly affected by the choice of median.

Conclusions:

• Practitioner-specific medians effectively correct for individual measurement biases in nuchal translucency assessment.
• The use of practitioner-specific medians enhances screening performance and aids in achieving desired detection rate goals.
• Individualized medians are essential for accurate and reliable prenatal screening outcomes.