Bestwick 2010.
| Clinical features and settings | Routine screening | |
| Participants | 22,746 participants UK ‐ 2 clinics January 2003 ‐ December 2008 Pregnant women Median maternal age 39 years (Down's syndrome) and 34 years (non‐Down's syndrome) 11‐13 and 14‐22 weeks' gestation |
|
| Study design | Retrospective cohort | |
| Target condition and reference standard(s) | Down's syndrome: 106 cases Reference standards: karyotyping or follow‐up to birth |
|
| Index and comparator tests | Maternal age First trimester NT, PAPP‐A and free ßhCG (details not reported) Second trimester AFP, uE3, free ßhCG and inhibin‐A (details not reported) |
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| Follow‐up | Data obtained from the Hospitals, the regional cytogenetic unit and the National Down Syndrome Cytogenetic Register | |
| Aim of study | To determine whether the SD of NT measurements has decreased over time and, if so, to revise the estimate and assess the effect of revising the estimate of the SD on the performance of antenatal screening for Down's syndrome | |
| Test characteristics | ||
| Reference standard used | ||
| 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 | No | Choice of reference standard depended on index test results |
| 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 |