Gasiorek‐Wiens 2001.

Clinical features and settings	Routine screening
Participants	21,959 participants Germany, Switzerland and Austria ‐ multicentre study June 1995‐May 2000 Pregnant women Median age 33 years (15‐49 years), 36.1% > 35 years Singleton pregnancies 10‐14 weeks' gestation
Study design	Prospective cohort
Target condition and reference standard(s)	Down's syndrome: 210 cases Reference standards: CVS, amniocentesis or follow‐up to birth
Index and comparator tests	Maternal age NT (FMF methods) Risk cut‐points of 1:100 and 1:300
Follow‐up	Follow‐up in 92.2% of women. Loss to follow‐up was due to miscarriage (n = 258), termination of pregnancy (n = 125) or absence of antenatal karyotyping (n = 1463). Only those with follow‐up information included in the study
Aim of study	To examine the effectiveness of screening for Down's syndrome using age and NT at 10‐14 weeks of gestation
Notes
Table of Methodological Quality
Item	Authors' judgement	Description
Representative spectrum? All tests	Yes	Routine screening of typical pregnant population
Acceptable reference standard? All tests	Yes	Karyotyping or follow‐up to birth
Partial verification avoided? All tests	Yes	All women received a reference standard
Differential verification avoided? All tests	No	Choice of reference standard depended on index test results
Incorporation avoided? All tests	Yes	Reference standard was independent of the index test
Reference standard results blinded? All tests	No	Reference standard interpreted with knowledge of index test results
Index test results blinded? All tests	Yes	Index test interpreted without knowledge of reference standard results
Relevant clinical information? All tests	Yes	Information available as would be in standard clinical practice
Uninterpretable results reported? All tests	Yes	Reported that NT successfully measured in all cases
Withdrawals explained? All tests	No	No details of withdrawals given