Spencer 1996.

Clinical features and settings	High‐risk referral for invasive testing.
Participants	429 participants: 29 cases and 400 controls. UK. Date not specified. Pregnant women. Singleton pregnancies. 14‐24 (cases) and 9‐22 (controls) weeks' gestation.
Study design	Case‐control study.
Target condition and reference standard(s)	Down's syndrome: 29 cases. Reference standards: amniocentesis or CVS.
Index and comparator tests	Urine free beta hCG (CIS immunoradiometric assay). Urinary beta core fragment (Ciba Corning diagnostics UGP enzyme immunoassay).
Follow‐up	100% karyotyping.
Aim of study	To evaluate whether free beta hCG is elevated in the urine of pregnancies affected by Down's syndrome and investigate whether urine free beta hCG may be used as possible screening 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 or CVS.
Partial verification avoided? All tests	Yes	All women had a reference standard.
Differential verification avoided? All tests	No	Women had different reference standards.
Incorporation avoided? All tests	Yes	Reference standard was independent of the index test.
Reference standard results blinded? All tests	Yes	Reference standard interpreted without 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.