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. 2017 Mar 15;2017(3):CD012599. doi: 10.1002/14651858.CD012599

Okun 2008 Integrated.

Clinical features and settings Routine screening
Participants 32,227 participants undergoing integrated screening (a separate cohort evaluated for first trimester screening)
January 2003 ‐ December 2005
Canada ‐ 2 hospitals
Pregnant women
Mean maternal age 32 years
11‐14 and 15‐18 weeks' gestation
Study design Prospective cohort
Target condition and reference standard(s) Down's syndrome: 86 affected cases
Reference standards: karyotyping or follow‐up to birth
Index and comparator tests Maternal age
First trimester NT (most sonographers had FMF certification)
First trimester free ßhCG and PAPP‐A (DSX Four Plate Automated ELISA Processing system, Dynex Technologies and DPC Immulite 2000 automated immunoassay analyser, Siemens Medical Solutions Diagnostics)
Second trimester hCG, AFP and uE3 (Time‐resolved fluoroimmunoassay, PerkinElmer AutoDelfia)
Risk cut‐point 1:200 or NT ≥ 3.5 mm
Results presented with and without adjustment for bias due to miscarriages (viability bias)
Follow‐up From cytogenetics databases in both Hospitals, the Canadian Institute for Health Information, labour and delivery databases, written and phone follow‐up with care providers and phone follow‐up with women after birth
Aim of study To evaluate the performance of integrated prenatal screening and first trimester combined screening for trisomy 21 in a large Canadian urban centre
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 Yes 2614 (8%) of women undergoing integrated screening did not return for the second trimester part of the test