Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithm
Background. Screening for trisomy 21 provides pregnant women with accurate risk information. Different algorithms are used to screen for trisomy 21 in South Africa (SA). The Fetal Medicine Foundation (FMF) provides software to screen for trisomy 21 in the first trimester by ultrasound or a comb...
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South African Medical Association
2023-11-01
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| Series: | South African Medical Journal |
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| Online Access: | https://samajournals.co.za/index.php/samj/article/view/885 |
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| author | L Pistorius C A Cluver I Bhorat L Geerts |
| author_facet | L Pistorius C A Cluver I Bhorat L Geerts |
| author_sort | L Pistorius |
| collection | DOAJ |
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Background. Screening for trisomy 21 provides pregnant women with accurate risk information. Different algorithms are used to screen for trisomy 21 in South Africa (SA). The Fetal Medicine Foundation (FMF) provides software to screen for trisomy 21 in the first trimester by ultrasound or a combination of ultrasound and biochemistry (combined screening), and requires regular and stringent quality control. With αlpha software, first trimester combined screening and screening with biochemistry alone in the first or second trimester are possible. The αlpha screening requires quality control of biochemical tests, but not of ultrasound measurements. Ideally, a screening test should have a high detection and a low screen positive rate. Despite the availability of these screening programmes, only a minority of infants with trisomy 21 are detected prenatally, raising questions about the effectiveness of screening.
Objectives. To determine the screen positive and detection rates of prenatal screening for trisomy 21 in the SA private healthcare system. Methods. Data from the three largest laboratories collected between 2010 and 2015 were linked with genetic tests to assess screen positive and detection rates. Biochemical screening alone with αlpha software (first or second trimester) and combined screening using either FMF or αlpha software were compared.
Results. One-third of an estimated 675 000 pregnancies in private practice in the 6-year study period underwent screening. There were 687 cases of trisomy 21 in 225 021 pregnancies, with only 239 (35%) diagnosed prenatally. The screen positive rates were 11.8% for first trimester biochemistry, 7.6% for second trimester biochemistry, 7.3% for first trimester FMF software ultrasound alone, 3.7% for combined first trimester screening with FMF software, and 3.5% for combined first trimester screening with αlpha software. The detection rates for a 5% false positive rate were 63% for first trimester biochemistry, 69% for second trimester biochemistry, 95% for combined first trimester screening with FMF software and 80% for combined first trimester screening with αlpha software. Detection and confirmation rates were highest with FMF software.
Conclusion. Screening with FMF software has a similar screen positive rate and better detection rate than screening with αlpha software. The low prenatal detection rate of trisomy 21 is mainly due to a low prevalence of screening. More research is needed in the SA setting to explore why screening and confirmatory testing after high-risk results are not performed in many pregnancies.
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| format | Article |
| id | doaj-art-a423f3f3f6da4acaab890cf1c401af17 |
| institution | Kabale University |
| issn | 0256-9574 2078-5135 |
| language | English |
| publishDate | 2023-11-01 |
| publisher | South African Medical Association |
| record_format | Article |
| series | South African Medical Journal |
| spelling | doaj-art-a423f3f3f6da4acaab890cf1c401af172025-02-10T12:26:40ZengSouth African Medical AssociationSouth African Medical Journal0256-95742078-51352023-11-011131110.7196/SAMJ.2023.v113i11.885Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithmL Pistorius0C A Cluver1https://orcid.org/0000-0002-0406-8964I Bhorat2L Geerts3Department of Obstetrics and Gynaecology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa, Panorama Perinatology, Mediclinic Panorama, Cape Town, South AfricaDepartment of Obstetrics and Gynaecology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa, Panorama Perinatology, Mediclinic Panorama, Cape Town, South AfricaDepartment of Obstetrics and Gynaecology, College of Health Sciences, University of KwaZulu-Natal, Durban, South AfricaDepartment of Obstetrics and Gynaecology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa Background. Screening for trisomy 21 provides pregnant women with accurate risk information. Different algorithms are used to screen for trisomy 21 in South Africa (SA). The Fetal Medicine Foundation (FMF) provides software to screen for trisomy 21 in the first trimester by ultrasound or a combination of ultrasound and biochemistry (combined screening), and requires regular and stringent quality control. With αlpha software, first trimester combined screening and screening with biochemistry alone in the first or second trimester are possible. The αlpha screening requires quality control of biochemical tests, but not of ultrasound measurements. Ideally, a screening test should have a high detection and a low screen positive rate. Despite the availability of these screening programmes, only a minority of infants with trisomy 21 are detected prenatally, raising questions about the effectiveness of screening. Objectives. To determine the screen positive and detection rates of prenatal screening for trisomy 21 in the SA private healthcare system. Methods. Data from the three largest laboratories collected between 2010 and 2015 were linked with genetic tests to assess screen positive and detection rates. Biochemical screening alone with αlpha software (first or second trimester) and combined screening using either FMF or αlpha software were compared. Results. One-third of an estimated 675 000 pregnancies in private practice in the 6-year study period underwent screening. There were 687 cases of trisomy 21 in 225 021 pregnancies, with only 239 (35%) diagnosed prenatally. The screen positive rates were 11.8% for first trimester biochemistry, 7.6% for second trimester biochemistry, 7.3% for first trimester FMF software ultrasound alone, 3.7% for combined first trimester screening with FMF software, and 3.5% for combined first trimester screening with αlpha software. The detection rates for a 5% false positive rate were 63% for first trimester biochemistry, 69% for second trimester biochemistry, 95% for combined first trimester screening with FMF software and 80% for combined first trimester screening with αlpha software. Detection and confirmation rates were highest with FMF software. Conclusion. Screening with FMF software has a similar screen positive rate and better detection rate than screening with αlpha software. The low prenatal detection rate of trisomy 21 is mainly due to a low prevalence of screening. More research is needed in the SA setting to explore why screening and confirmatory testing after high-risk results are not performed in many pregnancies. https://samajournals.co.za/index.php/samj/article/view/885screeningDown syndromealpha softwareFetal Medicine Foundationfetalultrasound |
| spellingShingle | L Pistorius C A Cluver I Bhorat L Geerts Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithm South African Medical Journal screening Down syndrome alpha software Fetal Medicine Foundation fetal ultrasound |
| title | Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithm |
| title_full | Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithm |
| title_fullStr | Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithm |
| title_full_unstemmed | Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithm |
| title_short | Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithm |
| title_sort | trisomy 21 screening with αlpha software and the fetal medicine foundation algorithm |
| topic | screening Down syndrome alpha software Fetal Medicine Foundation fetal ultrasound |
| url | https://samajournals.co.za/index.php/samj/article/view/885 |
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