Nicolaides 2005.
| Clinical features and settings | Routine screening | |
| Participants | 75,821 participants with available information on outcome UK ‐ Various hospitals and a fetal medicine centre June 1998 ‐ December 2003 Pregnant women Median age 31 years (13‐49 years) Singleton pregnancies 11‐13 weeks' gestation |
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| Study design | Prospective cohort | |
| Target condition and reference standard(s) | Down's syndrome: 325 cases Reference standards: amniocentesis or CVS (patients considered high risk based on screening). First trimester presence/absence of nasal bone, presence/absence of tricuspid regurgitation or normal/abnormal Doppler studies (patients of intermediate risk on first trimester screening and did not undergo CVS or amniocentesis. With the addition of information from these tests, if adjusted risk was high, CVS was performed). Follow‐up to birth |
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| Index and comparator tests | Maternal age First trimester NT (FMF methods) First trimester free ßhCG and PAPP‐A (Kryptor analyser, Brahms AG) Risk cut‐point 1:300 |
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| Follow‐up | Follow‐up data from cytogenetics laboratories, patients, GPs or maternity units where they delivered. Patients without follow‐up information due to miscarriage or termination (n = 490) or loss to follow‐up (n = 2117) were excluded from the study. | |
| Aim of study | To evaluate the performance of first trimester screening for trisomy 21 by a combination of maternal age, fetal NT and maternal serum free ßhCG and PAPP‐A. In addition, the impact of a new individual risk orientated 2‐stage approach to first trimester screening was examined | |
| 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 | Yes | 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 | Yes | Exclusions due to loss to follow‐up and missing information for women with miscarriages or terminations of pregnancy explained |