Fetal sonographic cardiothoracic ratio at midpregnancy as a predictor of Hb Bart disease.
The objective of this study is to evaluate the efficacy of sonographic cardiothoracic ratio at midpregnancy in predicting fetal hemoglobin Bart disease. Among 17,254 pregnant women screened for severe thalassemia between June 1994 and November 1998, 345 pregnant women at risk for having a fetus with hemoglobin Bart disease underwent ultrasonographic examination and cordocentesis at 18 to 21 weeks' gestation. Before cordocentesis, the cardiothoracic ratio was determined and recorded. The definite fetal diagnosis was based on fetal blood analysis with high performance liquid chromatography. Among 345 pregnancies in which sonographic examination and cordocentesis were performed, 70 fetuses were affected by hemoglobin Bart disease. The mean cardiothoracic ratio was significantly higher than that of unaffected fetuses (0.55 versus 0.45, Student's t-test, P<0.001). The sensitivity and specificity of the cardiothoracic ratio in prediction were calculated for various cutoff values. On the basis of the receiver operating characteristic curve, the best cutoff value was 0.50 (greater than 0.50 considered abnormal), giving the sensitivity of 98.6% and a specificity of 98.9%. In conclusion, the cardiothoracic ratio has very high accuracy in predicting hemoglobin Bart disease in pregnancies at risk. This finding suggests that invasive diagnostic method should be reserved for only the fetuses who have a cardiothoracic ratio of 0.5 or more; however, further studies are needed to confirm this observation.
Tongsong
T
T
Department of Obstetrics and Gynecology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
Wanapirak
C
C
Sirichotiyakul
S
S
Piyamongkol
W
W
Chanprapaph
P
P
D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging*; D005318:Fetal Heart / Q000000981:diagnostic imaging*; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D018566:Pregnancy, High-Risk; D012372:ROC Curve; D013909:Thorax / Q000000981:diagnostic imaging* / Q000196:embryology*; D016216:Ultrasonography, Prenatal; D017085:alpha-Thalassemia / Q000000981:diagnostic imaging*