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Ultraschall Med 2015; 36(05): 501-506
DOI: 10.1055/s-0034-1399285
Original Article
© Georg Thieme Verlag KG Stuttgart · New York

Suspicious Prenasal Skin Thickness-to-Nasal Bone Length Ratio: Prevalence and Correlation with Other Markers in Second and Third Trimester Fetuses with Down Syndrome

Das auffällige Verhältnis von präfrontaler Hautdicke und Nasenbeinlänge: Prävalenz und Korrelation mit anderen Markern bei Feten mit Trisomie 21 im zweiten und dritten Trimenon
A. Hagen
1   Obstetrics and Gynecology, Center for Prenatal Diagnosis and Human Genetics Kudamm-199, Berlin, Germany
,
M. Albig
1   Obstetrics and Gynecology, Center for Prenatal Diagnosis and Human Genetics Kudamm-199, Berlin, Germany
,
T. Keller
2   Statistik, ACOMED, Leipzig, Germany
,
M. Stumm
3   Human Genetics, Center for Prenatal Diagnosis and Human Genetics Kudamm-199, Berlin, Germany
,
M. Entezami
1   Obstetrics and Gynecology, Center for Prenatal Diagnosis and Human Genetics Kudamm-199, Berlin, Germany
› Author Affiliations
Further Information

Publication History

19 May 2014

10 February 2015

Publication Date:
19 June 2015 (online)

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Abstract

Purpose: To assess the prevalence and value of a suspicious prenasal skin thickness-to-nasal bone length ratio (PT/NB ratio) in comparison to other established markers in a large population of Down syndrome (DS) fetuses.

Materials and Methods: This was a retrospective study of 139 DS fetuses and 530 normal fetuses scanned after 14 + 0 weeks of gestation. To characterize diagnostic performance, we used the ROC curve approach. The presence or absence of a PT/NB ratio > 0.8 and 11 other markers were assessed in the group of DS fetuses. A correlation analysis was performed in order to investigate associations between PT/NB ratio and other markers.

Results: Among DS fetuses the median PT/NB ratio was 1.06 (IQR 0.729) and was significantly higher compared to normal fetuses with 0.62 (IQR 0.148), (p < 0.001). Gestational age had no influence on the PT/NB ratio. A PT/NB ratio > 0.8 had the highest prevalence of all markers with 89.2 % in the group of DS fetuses, 3 cases were negative for all markers and 3 cases were positive only for PT/NB ratio > 0.8. Marker-specific comparison between prevalences of a suspicious PT/NB ratio with respect to the presence or absence of other markers was statistically significant for hypoplastic NB and major anomalies (p < 0.05). Utilization of at least one of the following five markers was sufficient for detecting 136 out of 139 fetuses with trisomy 21: suspicious PT/NB ratio, hypoplastic NB, nuchal fold thickness, white spot, shortened femur.

Conclusion: The PT/NB ratio is one of the most powerful indicators of DS in the second trimester. It is objective to interpret, easy to measure, and is reproducible.

Zusammenfassung

Ziel: Untersuchung der Prävalenz einer auffälligen Ratio von präfrontaler Hautdicke und Nasenbeinlänge (PT/NB-Ratio) in einer größeren Population von Feten mit Down-Syndrom (DS) im zweiten und dritten Trimenon sowie die Beurteilung des Stellenwerts und der Korrelation gegenüber anderen etablierten Markern.

Material und Methoden: Es handelt sich um eine retrospektive Analyse von 139 Feten mit DS und 530 gesunden Feten ab 14 + 0 Schwangerschaftswochen. Die diagnostische Güte wurde mittels ROC-Kurven charakterisiert. Des Weiteren wurde die Prävalenz einer auffälligen PT/NB-Ratio (cut off > 0,8) und 11 anderer etablierter DS Marker bestimmt. Mit einer Korrelationsanalyse wurden mögliche Zusammenhänge einer auffälligen PT/NB-Ratio mit anderen der genannten Marker untersucht.

Ergebnisse: Bei Feten mit DS lag der Median der PT/NB-Ratio bei 1,06 (IQR 0,729) und damit signifikant höher als bei gesunden Feten mit 0,62 (IQR 0.148) (p < 0,001). Das Gestationsalter hatte keinen Einfluß auf die PT/NB-Ratio. Bei den Feten mit DS hatte eine PT/NB-Ratio > 0,8 die höchste Prävalenz aller Marker mit 89,2 %. In 3 Fällen von DS waren alle Marker negative. Gleichfalls in 3 Fällen war eine auffällige PT/NB-Ratio der einzige positive Marker. Bei der Untersuchung der Korrelation mit anderen Markern ergab sich eine signifikante Zunahme der Prävalenz für Fälle mit gleichzeitig bestehenden schweren Fehlbildungen oder bei Nachweis eines hypoplastischen Nasenbeins (p < 0,05). Bei 136 von 139 Feten war immer zumindest einer der folgenden Marker nachweisbar: PT/NB-Ratio > 0,8, hypoplastisches NB, Nackenödem, white spot, verkürzter Femur.

Schlussfolgerung: Die auffällige PT/NB-Ratio ist einer der wichtigsten Marker für das DS im 2. und 3. Trimenon. Er ist einfach zu messen, leicht reproduzierbar und unterliegt keiner subjektiven Interpretation.

Key words

prenasal skin thickness - nasal bone length - trisomy 21
 

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