Gasiorek‐Wiens 2010.

Clinical features and settings	Routine screening
Participants	4097 participants with complete data on pregnancy outcome Germany ‐ single examiner December 1997 ‐ November 2006 Pregnant women Singleton pregnancies Median age 35.1 years (range 13.2‐46.7 years) 11‐13 weeks' gestation
Study design	Cohort study
Target condition and reference standard(s)	Down's syndrome: 34 cases Reference standards: Karyotyping or follow‐up to birth
Index and comparator tests	Maternal age First trimester NT (FMF methods) Mixture model, Delta NT and multiple of the median methods
Follow‐up	Patient history and ultrasound results were entered into a database and pregnancy outcome or chromosomal results added as they became available 74 (1.8%) of women were excluded from the study because of incomplete follow‐up information
Aim of study	To validate the mixture model in a single operator dataset and to compare the detection rates for fetal chromosomal defects obtained from the mixture model with those obtained from either the delta NT or log multiple of the median approach
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	No	No details given for test failures/uninterpretable measurements
Withdrawals explained? All tests	No	No details of withdrawals given