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Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithm
L Pistorius1, C A Cluver2, I Bhorat3
1Department of Obstetrics and Gynaecology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa, Panorama Perinatology, Mediclinic Panorama, Cape Town, South Africa. lou@maternalfetal.co.za.
Summary
Prenatal screening for trisomy 21 in South Africa shows Fetal Medicine Foundation (FMF) software offers better detection rates than alpha software. Low screening uptake limits prenatal diagnosis effectiveness.
Area of Science:
- Prenatal diagnostics
- Genetics
- Public health
Background:
- Trisomy 21 screening provides crucial risk information to pregnant women.
- South Africa utilizes various algorithms for trisomy 21 screening.
- Current screening methods raise concerns about effectiveness due to low prenatal detection rates.
Purpose of the Study:
- To evaluate the screen positive and detection rates of prenatal screening for trisomy 21.
- To compare different screening algorithms within the South African private healthcare system.
Main Methods:
- Data from three major laboratories (2010-2015) were analyzed and linked with genetic tests.
- Biochemical screening (alpha software) and combined screening (FMF or alpha software) were compared.
- Screen positive and detection rates were assessed for various screening methods.
Main Results:
- Only 35% of trisomy 21 cases were diagnosed prenatally out of 225,021 pregnancies screened.
- Combined screening with FMF software achieved a 95% detection rate at a 5% false positive rate.
- FMF software demonstrated superior detection rates compared to alpha software.
Conclusions:
- FMF software offers comparable screen positive rates with superior detection for trisomy 21 compared to alpha software.
- Low screening uptake significantly impacts the overall prenatal detection rate of trisomy 21.
- Further research is needed to understand barriers to screening and confirmatory testing in South Africa.
