Thilaganathan 1999.
| Clinical features and settings | Routine screening | |
| Participants | 9802 participants UK ‐ district general hospital November 1994 to November 1998 Pregnant women Singleton pregnancies Mean age 29 years (15‐45 years) 10 to 14 weeks' gestation |
|
| Study design | Prospective cohort | |
| Target condition and reference standard(s) | Down's syndrome: 21 cases Reference standards: CVS (offered to patients considered high risk on screening) or follow‐up to birth |
|
| Index and comparator tests | Maternal age First trimester NT (transabdominally, Toshiba SSA‐250, Accuson 128XP/4 or Aloka 650CL with 3.5‐7.5 curvilinear transducers) |
|
| Follow‐up | Pregnancy outcomes from hospital records and general practitioners. Karyotype results or postnatal tests were provided by the local Regional Cytoenetics laboratory. The proportion of patients who were followed up is not reported (49 patients had not given birth at the time of analysis of outcomes) | |
| Aim of study | To evaluate the effectiveness of 10‐14 week NT measurement in routine ultrasounds screening for Down's syndrome | |
| 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 | Yes | Unsuccessful NT in 10.1% of patients |
| Withdrawals explained? All tests | Yes | Patients not included due to ineligibility described |