Bahado‐Singh 1999.

Clinical features and settings	High‐risk referral for invasive testing.
Participants	457 participants. USA. August 1996 ‐ June 1997. Pregnant women. Mean age 37.1 years. Singleton pregnancies. 15‐24 weeks' gestation.
Study design	Prospective cohort study.
Target condition and reference standard(s)	Down's syndrome: 13 cases. Reference standard: amniocentesis.
Index and comparator tests	Maternal age. Urinary ß core fragment (monoclonal antibody B210 assay, 2‐step sandwich method, standardised for creatinine). Urinary beta core fragment/total urinary oestriol ratio.
Follow‐up	100% karyotyping.
Aim of study	To evaluate Down's syndrome screening efficiency of a new algorithm of multiple urinary biochemical and ultrasound markers.
Notes
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	Amniocentesis.
Partial verification avoided? All tests	Yes	All women received a reference standard.
Differential verification avoided? All tests	Yes	All women received the same reference standard.
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.