title: A new strategy for prenatal diagnosis of homozygous alpha(0)-thalassemia.
abstract: OBJECTIVE
  We have shown previously that ultrasound examination performed by one experienced operator can be useful to exclude homozygous alpha(0)-thalassemia in a tertiary referral center. This study aimed to determine whether the technique was still applicable when performed by several operators and in different centers.
  
  
  METHODS
  At the Maternal and Neonatal Hospital of Guangzhou (MNH) and Tsan Yuk Hospital of Hong Kong (TYH), women at risk of homozygous alpha(0)-thalassemia were given the option of a non-invasive approach (using serial ultrasound examinations at 12-15, 16-20 and 25-30 weeks' gestation) to exclude an affected pregnancy. The fetal cardiothoracic ratio (CTR) was measured at each of these examinations and the placental thickness was measured at 12-15 weeks' gestation. The operators of MNH received training on the ultrasound examination techniques at TYH and the quality of the subsequent ultrasound examinations was checked regularly. The final diagnosis of homozygous alpha(0)-thalassemia was confirmed using an invasive test.
  
  
  RESULTS
  Of 832 at-risk pregnancies studied in the two hospitals, 168 (20.2%) were affected. The overall sensitivity and specificity of the non-invasive approach was 100% and 95.6%, respectively. At MNH, the need for an invasive test was reduced by 80.8%, and all the affected pregnancies were diagnosed before 24 weeks' gestation. The results achieved at MNH were comparable with those at TYH. The at-risk pregnancies including the affected ones presented at a more advanced gestational age at MNH. At each hospital, one affected pregnancy was missed at the 12-week scan but this was subsequently detected at the 15-18-week scan.
  
  
  CONCLUSIONS
  This non-invasive approach to exclude homozygous alpha(0)-thalassemia can be applicable when it is performed by several operators and in different centers.
authors.affiliation: Department of Obstetrics and Gynaecology, The University of Hong Kong, Queen Mary Hospital, Guangzhou, Guangdong, China. Leungky1@ha.org.hk
authors.forename: K Y
authors.initials: KY
authors.lastname: Leung
authors.forename: C
authors.initials: C
authors.lastname: Liao
authors.forename: Q M
authors.initials: QM
authors.lastname: Li
authors.forename: S Y
authors.initials: SY
authors.lastname: Ma
authors.forename: M H Y
authors.initials: MH
authors.lastname: Tang
authors.forename: C P
authors.initials: CP
authors.lastname: Lee
authors.forename: V
authors.initials: V
authors.lastname: Chan
authors.forename: Y H
authors.initials: YH
authors.lastname: Lam
mesh_terms: D006332:Cardiomegaly / Q000150:complications / Q000000981:diagnostic imaging; D004247:DNA / Q000032:analysis; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006720:Homozygote; D006801:Humans; D011247:Pregnancy; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000379:methods* / Q000592:standards; D017085:alpha-Thalassemia / Q000150:complications / Q000000981:diagnostic imaging*
chemical_list: D006454:Hemoglobins; D004247:DNA