NEW YORK (Reuters Health) - The absence of a fetal nasal bone is a useful adjunct to standard first-trimester markers for Down syndrome, according to Italian and US researchers.
While fetal screening for bone absence appears to be useful, various criteria have been used to assess the presence or absence of nasal bone, Dr. Francesco Orlandi, Centro di Diagnosi Prenatale, Palermo, and colleagues note in the April issue of the American Journal of Obstetrics and Gynecology.
In the study, the “fetus was considered to have an absent nasal bone only if there was no evidence at all of present nasal bone, while in previous studies the nasal bone was classified as present when there was evidence of a thin echogenic line under the skin of the nose,” Dr. Orlandi told Reuters Health.
Using this criterion, the researchers assessed nasal bones in 2411 fetuses of 11.4 to 13.6 gestational weeks, including 15 with Down syndrome. Simulation studies were conducted to evaluate detection rates with a combined first-trimester screening protocol including nasal bone assessment.
“There were 9 of 2396 (0.4%) unaffected cases with absent nasal bone...and 8 of 15 (53.3%) Down syndrome,” they report.
Without nasal bone assessment, standard screening had an 87% detection rate and a 4.3% false-positive rate. Incorporating nasal bone assessment increased the detection rate to 90% and reduced the false-positive rate to 2.5%.
If these data are confirmed, concluded Dr. Orlandi, “the use of a strict, and more reproducible, criterion to determine nasal bone absence will lead to a smaller number of false positive cases and may simplify the implementation” of the approach in first trimester screening.
Source: Am J Obstet Gynecol 2005;192:1107-1011. [ Google search on this article ]
MeSH Headings:Diagnosis: Diagnostic Techniques, Obstetrical and Gynecological: Prenatal Diagnosis: Diagnostic Techniques and Procedures: Analytical, Diagnostic and Therapeutic Techniques and EquipmentCopyright © 2002 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.
