eprintid: 10127016 rev_number: 16 eprint_status: archive userid: 608 dir: disk0/10/12/70/16 datestamp: 2021-05-05 16:30:32 lastmod: 2022-01-12 23:56:27 status_changed: 2021-05-05 16:30:32 type: article metadata_visibility: show creators_name: Vale, SH creators_name: Huttly, WJ creators_name: Wald, NJ title: Antenatal screening for Down’s syndrome: Revised nuchal translucency upper truncation limit due to improved precision of measurement ispublished: inpress divisions: UCL divisions: B02 divisions: DD4 note: This article is distributed under the terms of the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/) which permits any use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access pages (https://us.sagepub.com/en-us/nam/open-access-at-sage). abstract: Objective: To determine whether the improved precision of nuchal translucency (NT) measurement used in antenatal screening for Down’s syndrome observed over time as evidenced by a decrease in the multiple of the median (MoM) standard deviation requires a modification to the NT MoM truncation limits to maintain accurate risk estimation. Methods: Probability plots were derived from the measurements of NT MoM values used in a 2018 audit of 22,362 unaffected pregnancies. The plots were used to determine whether the NT MoM upper truncation limit should be lowered. Validation plots were used to assess the screening accuracy of Down’s syndrome risk estimates calculated from observed NT MoM values in the 22,362 unaffected pregnancies and 69 Down’s syndrome pregnancies for original and revised NT MoM truncation limits. Results: Probability plots indicated that with improved precision of NT measurements, there was deviation from a Gaussian distribution at less high MoM values than with less precise measurements. Validation plots showed that using the current NT MoM upper truncation limit of 2.5 MoM with improved precision NT measurements overestimates the Down’s syndrome risk (median risk in highest risk category expressed as an odds was 53.3:1 and observed prevalence was 1:1.1). The large discrepancy was corrected by changing the NT upper truncation limit to 2.0 MoM (median risk in highest risk category expressed as an odds was 1:1.78 and observed prevalence 1:2.7). Conclusion: The NT MoM upper truncation limit should be reduced from 2.5 to 2.0 MoM. date: 2020-07-01 date_type: published official_url: https://doi.org/10.1177/0969141320937321 oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 1832970 doi: 10.1177/0969141320937321 lyricists_name: Wald, Nicholas lyricists_id: NJWAL52 actors_name: Zahnhausen-Stuber, Petra actors_id: PMZAH20 actors_role: owner full_text_status: public publication: Journal of Medical Screening citation: Vale, SH; Huttly, WJ; Wald, NJ; (2020) Antenatal screening for Down’s syndrome: Revised nuchal translucency upper truncation limit due to improved precision of measurement. Journal of Medical Screening 10.1177/0969141320937321 <https://doi.org/10.1177/0969141320937321>. (In press). Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10127016/1/0969141320937321.pdf