{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,8,29]],"date-time":"2025-08-29T10:23:36Z","timestamp":1756463016131},"reference-count":20,"publisher":"Wiley","issue":"3","license":[{"start":{"date-parts":[[2012,8,22]],"date-time":"2012-08-22T00:00:00Z","timestamp":1345593600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["obgyn.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Ultrasound in Obstet &amp; Gyne"],"published-print":{"date-parts":[[2012,9]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Objective<\/jats:title><jats:p>To prospectively evaluate the performance of first\u2010trimester combined screening for trisomy 21 using the biochemical markers pregnancy\u2010associated plasma protein\u2010A (PAPP\u2010A) and free beta\u2010human chorionic gonadotropin (free \u03b2\u2010hCG) obtained before and at the time of the nuchal translucency (NT) scan.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>Three fetal medicine departments in Denmark participated in the study. Screening for trisomy 21 was set up as a two\u2010step approach with blood sampling performed before the NT scan (early sample) and again at the time of the NT scan (late sample). PAPP\u2010A and free \u03b2\u2010hCG were measured on both the early and late samples. Age\u2010standardized detection and false\u2010positive rates for different screening protocols were calculated.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>We collected two blood samples in 27 pregnancies affected by trisomy 21 and in 3891 control pregnancies. The early samples were taken between gestational ages 8 + 0 and 13 + 6 weeks, and the late samples between 11 + 3 and 14 + 6 weeks. The median interval between the samples was 17 (range, 1\u201340) days. We found a significantly better estimated screening performance when using early sampling <jats:italic>vs<\/jats:italic> late sampling (<jats:italic>P<\/jats:italic> &lt; 0.05). With a risk cut\u2010off of 1 in 100, at the time of the risk assessment the estimated detection and false\u2010positive rates when using the early sample were 91% (95% CI, 81\u201398%) and 1.6% (95% CI, 1.3\u20132.0%), respectively. For fixed false\u2010positive rates the highest detection rates were achieved using both blood samples. When comparing early sampling <jats:italic>vs<\/jats:italic> double sampling there was no significant difference in screening performance.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>In combined first\u2010trimester screening for trisomy 21, use of early sampling with measurement of PAPP\u2010A and free \u03b2\u2010hCG before the time of the NT scan can optimize screening performance. Using maternal serum markers obtained both before and at the time of the NT scan has the potential to further improve performance, but larger studies are needed to confirm this potential. Copyright \u00a9 2012 ISUOG. Published by John Wiley &amp; Sons, Ltd.<\/jats:p><\/jats:sec>","DOI":"10.1002\/uog.12266","type":"journal-article","created":{"date-parts":[[2012,7,19]],"date-time":"2012-07-19T05:24:42Z","timestamp":1342675482000},"page":"276-281","update-policy":"http:\/\/dx.doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Prospective study evaluating performance of first\u2010trimester combined screening for trisomy 21 using repeat sampling of maternal serum markers PAPP\u2010A and free \u03b2\u2010hCG"],"prefix":"10.1002","volume":"40","author":[{"given":"C.","family":"Ekelund","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"D.","family":"Wright","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"S.","family":"Ball","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"I.","family":"Kirkegaard","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"P.","family":"N\u00f8rgaard","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"S.","family":"S\u00f8rensen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"L.","family":"Friis\u2010Hansen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"F. 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