Brizot 2001.

Clinical features and settings	Routine screening
Participants	2996 participants Brazil ‐ University Hospital Estimated date of delivery pre December 1999 Pregnant women Median age 28 years (13‐46 years), 19.4% ≥ 35 years Singleton pregnancies 10‐14 weeks' gestation (mean 12 weeks)
Study design	Prospective cohort
Target condition and reference standard(s)	Down's syndrome: 10 cases Reference standards: antenatal karyotyping (5.9% of pregnancies: 62% of high‐risk, 29% of medium‐risk and 3% of the low‐risk women) or follow‐up to birth (85.3% of women)
Index and comparator tests	Maternal age First trimester (10‐14 weeks) NT Risk cut‐off 1:300
Follow‐up	85.3% of women were followed up to birth. Of these, 65 were spontaneous miscarriages or intrauterine death with no karyotyping
Aim of study	To assess the detection rate of chromosomal abnormalities using NT
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	Unclear	Unclear if 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