Browsing by Subject "false negative"

In Finland, the primary screening method for chromosomal abnormalities is the first trimester combined screening. The aim is to find pregnancies with an increased risk for the most common chromosomal abnormalities, trisomies 13, 18 or 21. Objective: When a person with the condition screened for gets a negative result, it’s referred to as a false negative. The objective of this study was to find common characteristics in false negative cases and compare them to those of true positives to see if there’s a significant difference. Methods: This is a retrospective study of pregnancies between 2014 and 2016 that ended in a birth of a neonate with trisomy 13, 18 or 21. In this study we focused on the neonates with trisomy 21. A risk figure of 1:250 was used as the cut-off value for trisomy 21. There were 14 false negative cases and 119 true positive cases that qualified for our study. The parameters analyzed were maternal age, gestational age at blood tests, biochemical markers PAPP-A (MoM) and hCG (MoM), gestational age at ultrasound and nuchal translucency. They were statistically analyzed. Results: By using logistic regression, we found that the most powerful discriminating factor between false negative and true positive cases was nuchal translucency, accounting for 47.6% of false negatives. The second most powerful factor was PAPP-A MoM explaining 15.2%. Maternal age explained 11.9% and hCG MoM 11.1%. Conclusion: All the factors except for gestational age accounted for a statistically significant proportion of false negatives. The most powerful discriminating factor between false negatives and true positives was nuchal translucency. 14.2% of the discrimination remains unknown to us. Since nuchal translucency is the most powerful discriminating factor, it is essential to focus on its correct measurement.