Maternal weight correction for alpha-fetoprotein: mathematical truncations revisited

Area of Science:

• Biochemistry
• Prenatal Diagnostics
• Medical Screening

Background:

• Alpha-fetoprotein (AFP) testing is a crucial component of prenatal screening.
• Current maternal weight correction methods for AFP testing were established two decades ago.
• The appropriateness of existing weight correction protocols requires re-evaluation.

Purpose of the Study:

• To assess the continued validity of maternal weight correction for AFP testing.
• To determine the optimal maternal weight cutoff for AFP measurement adjustments.
• To enhance the uniformity and accuracy of AFP screening across different maternal weights.

Main Methods:

• Analysis of 44,951 AFP screening cases from a single laboratory.
• Division of AFP measurements by maternal weight.
• Categorization of results into high (≥2.5 multiples of the median - MOM) and low (<0.4 MOM) levels.
• Comparison of AFP distribution using different maternal weight truncation points (200 lbs. vs. 250 lbs.).

Main Results:

• Without weight correction, higher maternal weight is associated with lower AFP levels.
• Truncating maternal weight at 200 lbs. yields more uniform AFP distributions compared to a 250 lbs. cutoff.
• A 200 lbs. cutoff optimizes the distribution of both high and low AFP values, reducing overcompensation seen with a 250 lbs. cutoff.

Conclusions:

• The existing maternal weight correction for AFP testing is outdated.
• A maternal weight cutoff of 200 lbs. provides a more equitable and accurate distribution of AFP test results.
• Implementing a 200 lbs. cutoff can improve the reliability of prenatal screening.