Otaño 2002.

Clinical features and settings	High‐risk referral for invasive testing
Participants	194 participants Argentina October 2001 ‐ January 2002 Pregnant women Median age 36 years (19‐44 years) Singleton pregnancies 11‐14 weeks' gestation
Study design	Prospective cohort
Target condition and reference standard(s)	Down's syndrome: 5 cases Reference standard: CVS
Index and comparator tests	First trimester nasal bone assessment (frontal saggital section of the fetal face. Angle of insonation of fetal nose close to 90 degree angle)
Follow‐up	100% karyotyping
Aim of study	To evaluate the association of nasal bone on ultrasound and Down's syndrome fetuses at 11‐14 weeks' gestation
Notes	States in text that there were 6 cases of trisomy 21
Table of Methodological Quality
Item	Authors' judgement	Description
Representative spectrum? All tests	Yes	Selective testing of high‐risk women as done in practice
Acceptable reference standard? All tests	Yes	CVS
Partial verification avoided? All tests	Yes	All women received a reference standard
Differential verification avoided? All tests	Yes	All women had the same reference standard
Incorporation avoided? All tests	Yes	Reference standard was independent of the index test
Reference standard results blinded? All tests	Unclear	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	Unsuccessful nasal bone assessment in 6%
Withdrawals explained? All tests	No	No details of withdrawals given