Orlandi 2005.

Clinical features and settings	Routine screening
Participants	2411 participants Italy Dates not reported Pregnant women Median age 30.5 years (SD 8.2) First trimester (gestational weeks not reported)
Study design	Retrospective cohort
Target condition and reference standard(s)	Down's syndrome: 15 cases Reference standard: not reported
Index and comparator tests	Maternal age First trimester nasal bone assessment (FMF methods) First trimester NT, free ßhCG and PAPP‐A Data from other studies used to generate statistical parameters to estimate performance of first trimester screening with and without nasal bone evaluation) Risk cut‐point 1:250
Follow‐up	No details reported for any follow‐up to birth
Aim of study	To determine the benefit of including nasal bone assessment in addition to standard first trimester markers as a screening test for Down's syndrome
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	Unclear	Unclear if the choice of reference standard depended on screening results
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	No	No details given for test failures/uninterpretable measurements
Withdrawals explained? All tests	No	No details of withdrawals given