Can Variable Plasma Volume Alterations Affect the Efficiency of the First Trimester Screening Test?

Area of Science:

• Maternal-Fetal Medicine
• Biochemistry
• Genetics

Background:

• First trimester screening is crucial for detecting fetal aneuploidy.
• Plasma volume alterations can influence biochemical marker levels.
• Hematocrit is a potential indicator of plasma volume changes.

Purpose of the Study:

• To evaluate the impact of hematocrit-determined plasma volume changes on first trimester screening biochemical parameters.
• To assess the relationship between hematocrit and false positive screening results.

Main Methods:

• 1,424 pregnant women in their first trimester were studied.
• Included ultrasonographic Nuchal Translucency measurement and serum free β-hCG and PAPP-A.
• Complete blood count was performed to assess hematocrit and rule out anemia.

Main Results:

• Serum hematocrit (Hct) significantly predicted false positive screening results (AUC: 0.839, p < 0.001).
• An optimal Hct cutoff of 30.2% demonstrated 85% sensitivity and 75% specificity for identifying false positives.
• 1.5% of the total cohort (21/1424) received false positive results.

Conclusions:

• Plasma volume alterations, reflected by hematocrit, can affect biochemical markers used in first trimester aneuploidy screening.
• Hematocrit levels may contribute to false positive results, necessitating careful interpretation.
• Further research is warranted to refine screening protocols considering plasma volume variations.