Table 9.8First-trimester screening for Down’s syndrome only

StudyRozenberg et al. (2006)778Avgidou et al. (2005)781Crossley et al. (2002)767
Type of studyProspective cohortProspective cohortProspective cohort
Year of publication200620052002
Period2001–20021999–20012 years
Setting10 perinatal units, France1 hospitals, 1 fetal medicine unit, UK15 maternity units, UK
Study populationUnselected (in a health authority)Selected (48.5 % ≥ 35 years)Unselected (for routine antenatal care)
ExclusionsAdequately describedAdequately describedNot applicable (100% follow-up)
Test conductedCombinedCombinedCombined
Monitoring of test qualityAdequateAdequateInadequate (NT in 73% of study population) (34/45 DS cases had combined test)
Validated reference standardYes (prenatal karyotype, pregnancy records)Yes (prenatal karyotype, pregnancy records)Yes (prenatal karyotype, pregnancy records)
Sample size (% of study population)14 380 (96.3%)30 564 (95.8%)17 229 (100%)
Maternal ageMedian 30.7 years, 25th to 75th centile 28–33.9 yearsMedian 34 years, range 15–49 yearsMedian 29.9 years, range 15–49 years
Number of DS cases (prevalence)51 (0.34%)196 (0.64%)45 (0.57%)
Results
Diagnostic accuracy (95% CI)Observed results:
DR 79.6%; FPR 2.7%; risk cut-off 1 : 250
Estimated results:
DR 90.3%; FPR 5% (fixed); risk cut-off ≥ 1 in 300
Observed results:
DR 82% (95% CI 65–93%) with 34 cases;
FPR 5%; risk cut-off 1 : 250
Evidence levelIbIIII
CommentsThis study also evaluated the diagnostic value of ‘first-trimester combined test followed by routine second-trimester ultrasound screening at 20–22 weeks for all the subjects’ and the results showed DR of 89.7% with FPR of 4.2%. The 20–22 weeks scan was considered positive if at least one major structural malformation was present or if nuchal fold was more than 6 mm. A cost analysis was also performed.The combined test could not be performed in all women and NT was done in 73% of the study population. 34 of 45 DS cases had completed screening. Considering the entire series of affected pregnancies, DR is reduced to 62%.

DR = detection rate; DS = Down’s syndrome; FPR = false positive rate; NT = nuchal translucency.

From: 9, Screening for fetal anomalies

Cover of Antenatal Care
Antenatal Care: Routine Care for the Healthy Pregnant Woman.
NICE Clinical Guidelines, No. 62.
National Collaborating Centre for Women's and Children's Health (UK).
London: RCOG Press; 2008 Mar.
Copyright © 2008, National Collaborating Centre for Women’s and Children’s Health.

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