Bahado‐Singh 1999a.

Clinical features and settings	High‐risk referral for invasive testing.
Participants	926 participants. USA. November 1995 ‐ March 1999. Pregnant women. Singleton pregnancies. 15‐24 weeks' gestation. Euploid/Down's karyotype only.
Study design	Prospective cohort study.
Target condition and reference standard(s)	Down's syndrome: 21 cases. Reference standard: amniocentesis.
Index and comparator tests	Maternal age. Second trimester urinary ß core fragment (Spot specimens of urine ‐ 2‐step sandwich assay B120 monoclonal antibody). Second trimester serum AFP. Frozen serum samples tested for second trimester uE3 and free ßhCG (details of serum testing methods not given).
Follow‐up	100% karyotyping.
Aim of study	To compare Down's syndrome screening efficiency of elevated maternal urine level of beta core fragment with that of a traditional serum triple test.
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 had 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.