Der combined test im ersten Schwangerschaftstrimenon bei 3316 nicht selektierten Schwangeren zur Diagnostik des M. Down[1]

Zusammenfassung

Hintergrund Die hohe pränatale Entdeckungsrate (ER) des Down-Syndroms, die durch die Messung der Nackentransparenz (NT) in der Frühschwangerschaft erzielt wird, wird durch die Kombination mit Plazentahormonen (PAPP-A, fβHCG) und dem mütterlichen Alter noch gesteigert („combined-test”). Wie hoch ist die ER des „combined-tests” in einem Kollektiv unselektierter, nicht zugewiesener Schwangerer bei einer Falschpositivenrate (FPR) von ca. 5 %.

Material und Methode Bei allen Frauen mit Einlingsschwangerschaften wurde im Zeitraum vom 1. 12. 97 - 31. 12. 99 zwischen der 10. und 13. Schwangerschaftswoche (Scheitelsteißlänge 3570 mm) die NT, das PAPP-A und das fβHCG gemessen. Die Berechnung des individuellen Down-Risikos erfolgte mit dem Programm Alpha, Version 5aa (Logical medical systems, London).

Ergebnisse Der Test wurde bei 3316 Schwangeren durchgeführt. 9 der 10 Downschwangerschaften, die in diesem Zeitraum auftraten, konnten damit entdeckt werden. 137 Frauen waren testpositiv, hatten aber keine Downschwangerschaft (FPR von 4,1 %).

Schlussfolgerungen Der „combined-test” ist auch in einem „low-risk”-Kollektiv ein ausgezeichneter Test zur Entdeckung des M. Down.

Diskussion Das ständig steigende Durchschnittsalter der Schwangeren würde bei Anwendung der Altersamniozentese die ER zwar moderat anheben, das aber zum Preis stark vermehrter Eingriffe und Fehlgeburten. Mit dem „combined-test” kann man die ER des M. Down bei viel geringeren FPR (ca. 5 %) weitaus deutlicher steigern.

The high detection rate (DR) for Down syndrome pregnancies which can be achieved by measuring fetal nuchal translucency (NT) early in pregnancy can be improved by combining it with placental hormones (PAPP-A, fβhCG) and maternal age (“combined test”). In this study we wanted to assess the DR using the “combined test” in an unselected population of self-referred pregnant women at a false positive rate (FPR) of about 5 %.

Materials and Methods NT, PAPP-A, fβhCG and maternal age were measured in all women with singleton pregnancies who booked for delivery in our hospital from 1. 12. 97 to 31. 12. 99 and who were between 10 and 13 completed weeks of gestation (crown-rump-length 35 - 70 mm). Calculation of the specific Down risk was done with the computer program Alpha, Version 5aa (Logical medical systems, London).

Results A total of 3316 women were tested. Out of 10 Down pregnancies, which occurred in this period of time 9 could be detected with the test. 137 women had a positive test result but a non-Down pregnancy (FPR 4.1 %).

Conclusions The combined test is an excellent test for the detection of Down syndrome pregnancies in a low-risk population.

Discussion The constant increase in maternal age at the time of delivery can also lead to an improved DR if a simple age dependant protocol for Down-detection is used, but only at the price of a much higher number of amniocenteses and subsequent abortions. The DR for Down syndrome can be increased much more markedly using the “combined test” at a much lower FPR (∼ 5 %).

Schlüsselwörter

Erstes Trimenon - Down Screening - combined test

Key words

First trimenon - down screening - combined test

1 Eingang: 16. 8. 2000
Angenommen nach Revision: 23. 11. 2000

Literatur

1 Eingang: 16. 8. 2000
Angenommen nach Revision: 23. 11. 2000

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