Open Access Research article

Screening for hemoglobin Bart’s disease among fetuses at risk at mid-pregnancy using the fetal cardiac diameter to biparietal diameter ratio

Nopamas Thathan, Kuntharee Traisrisilp, Suchaya Luewan, Kasemsri Srisupundit, Fuanglada Tongprasert and Theera Tongsong*

Author Affiliations

Department of Obstetrics and Gynecology, Faculty of Medicine Chiang Mai University, Chiang Mai 50200, Thailand

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BMC Pregnancy and Childbirth 2014, 14:230  doi:10.1186/1471-2393-14-230

Published: 16 July 2014

Abstract

Background

All sonomarkers used to screen for fetal hemoglobin (Hb) Bart’s disease need high expertise, preventing them from being widely used. Fetal cardiac diameter to biparietal diameter (C/B) ratio is a simple marker which has never been evaluated for its effectiveness. Therefore, we conducted this study to evaluate the effectiveness of C/B ratio in predicting fetal Hb Bart’s disease among fetuses at risk.

Methods

Fetuses at risk of Hb Bart’s disease scheduled for diagnostic cordocentesis at 18 to 22 weeks of pregnancy were prospectively enrolled. All underwent ultrasound for fetal biometry and cardio-STIC acquisition for subsequent off-line analysis. Cardio-STIC volume datasets (VDS) were analyzed for cardiac diameter measurement and C/B ratio was calculated by the authors who did not know the fetal diagnosis. Final diagnosis of Hb Bart’s disease was based on fetal blood Hb typing.

Results

Of 131 pregnancies enrolled to the study, 11 were excluded because of poor quality VDS. The remaining 120 were available for analysis. C/B ratio was significantly higher in the fetuses with Hb Bart’s disease than that in the unaffected ones (53.16% vs 41.68%, P < 0.001). C/B ratio could detect fetuses with Hb Bart’s disease with sensitivity of 91.5% and specificity of 77.6% (AUC ROC 0.929), using a cut-off point of greater than 45%.

Conclusions

Among fetuses at risk, C/B ratio measurement at mid-pregnancy, using cut-off point of 45%, could effectively differentiate fetuses with Hb Bart’s disease from unaffected fetuses.

Keywords:
Spatio-temporal image correlation (STIC); 4D-ultrasound; Cardiac diameter; Biparietal diameter; Hb Bart’s disease; Homozygous alpha-thalassemia-1 disease