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Age independent first trimester screening for Down syndrome: improvement in test performance
M A J Engels1, J W R Twisk, M A Blankenstein
1Department of Obstetrics and Gynaecology, VU University Medical Center, Amsterdam, the Netherlands. m.engels@vumc.nl
Prenatal Diagnosis
|May 18, 2013
Summary
The absolute risk (AR) method for Down syndrome screening offers comparable true prediction rates to the first trimester combined test (FCT) but significantly reduces false predictions. This approach may improve screening efficiency and uptake across all maternal ages.
Area of Science:
- Prenatal diagnostics
- Maternal-fetal medicine
- Genetics
Background:
- First trimester combined test (FCT) is a standard screening for Down syndrome.
- Screening performance can vary with maternal age.
- Absolute risk (AR) method is an alternative approach.
Purpose of the Study:
- To compare the screening performance of the absolute risk (AR) method versus the first trimester combined test (FCT) for Down syndrome.
- To evaluate performance across different maternal age groups.
Main Methods:
- Retrospective analysis of 32,448 first trimester combined tests (FCT).
- Absolute risk (AR) was calculated as final risk divided by maternal age risk.
Main Results:
- Both methods showed comparable likelihood of true predictions across all maternal ages.
- The AR method detected two additional Down syndrome cases in women under 30.
- The AR method missed three cases in women aged 36 and above.
- The AR method significantly decreased the likelihood of false predictions overall and in older age groups (41-45 years), but increased it in younger women (≤25 years).
Conclusions:
- The absolute risk (AR) method provides a similar true prediction rate to the FCT while significantly reducing false positive results.
- This reduction in false positives is expected to decrease the number of invasive diagnostic tests performed.
- The AR method may clarify screening performance differences across maternal ages, potentially increasing FCT uptake and improving overall screening policy efficiency.
