De Graaf 1999.
| Clinical features and settings | High‐risk referral for invasive testing | |
| Participants | 292 participants (207 participants before 14 weeks' gestation) The Netherlands ‐ single centre 19 84‐1997 Pregnant women Cases: 37 with Down's syndrome Controls: 255 matched 5:1 with cases for maternal age (within 2 years), gestational age (within 2 weeks) and duration of sample storage (within 2 months) 9‐15 weeks' gestation (in a few cases, blood samples for serum testing taken at 15‐19 weeks) |
|
| Study design | Case‐control study | |
| Target condition and reference standard(s) | Down's syndrome: 37 cases (24 affected pregnancies in women with NT testing enrolled before 14 weeks' gestation) Reference standards: CVS and amniocentesis |
|
| Index and comparator tests | Maternal age NT (FMF methods) with cut‐off > 3 mm Frozen serum samples tested for: First trimester free ßhCG and AFP (DELFIA dual labelled time resolved fluorescent assay) First trimester serum PAPP‐A (DELFIA research assay (CR61‐105)) First trimester serum AFP |
|
| Follow‐up | 100% karyotyping | |
| Aim of study | To determine the expected detection rate and false positive rate for Down's syndrome achievable by early pregnancy screening with combined measurements of serum PAPP‐A, free ßhCG and fetal nuchal translucency, with the addition of AFP | |
| 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 | Karyotyping |
| Partial verification avoided? All tests | Yes | All women had a reference standard |
| Differential verification avoided? All tests | Yes | All women had karyotyping |
| Incorporation avoided? All tests | Yes | Index test did not form part of the reference standard |
| Reference standard results blinded? All tests | No | Reference standard interpreted without knowledge of index test results |
| Index test results blinded? All tests | Unclear | Unclear if 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 | In 11 controls, failed to measure NT |
| Withdrawals explained? All tests | No | No details of withdrawals given |