OC16.02: *Improving the early detection of spina bifida using first trimester sonographic markers: diagnostic accuracy based on 480,000 examinations

To determine the diagnostic accuracy of first trimester ultrasound for the detection of spina bifida (SB); and understand the role of cranial sonographic markers in improving screening performance, including visualization or measurement of intracranial translucency (IT), brainstem (BS) to brainstem-occipital bone (BSOB) ratio or cisterna magna (CM). We evaluated the diagnostic accuracy of screening for SB (open and closed SB individually, and as composite) using data that was extracted from all studies assessing SB detection at 11-14 weeks gestation identified from an electronic search (Jan 2008 – Aug 2022). Meta-analysis (random-effects model) was undertaken and secondary analyses based on imaging protocols used by individual studies. An evaluation of common markers for SB was undertaken using pair-wise comparisons (chi-squared tests) of detection rates between studies. There were 488,707 fetuses of which 220 were affected by SB, (prevalence: 6.9/1000 (95% CI 5.0-9.2), from 46 studies). Overall detection rate (DR) was 50.3% (40.3 – 60.3), with specificity of 100.0% (100.0-100.0) and a positive predictive value of 89.5% (83.4 – 94.3). Significant differences in DR from five protocol subgroups were demonstrated (p < 0.0001, see figure 1). There were no statistically significant differences in DR between studies using a qualitative vs. quantitative assessment of markers (i.e. visual assessment vs. measurement, p = 0.11); using a single marker vs. multiple markers (p = 0.30); or using IT vs. BS/BSOB alone (p = 0.52). Beyond evaluation of the fetal spine, first trimester detection of spina bifida can be optimised by including sonographic assessment of cranial markers of the posterior fossa. Evaluation of the classic “three lines – four space view” significantly improves SB detection. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.