title: Systematic review of the clinical prediction rules for the calculation of the risk of Down syndrome based on ultrasound findings in the second trimester of pregnancy.
abstract: OBJECTIVE
  The objective of this article is to systematically review the various published clinical prediction rules used to calculate the risk of Down syndrome (DS) after carrying out an ultrasound in the second trimester of pregnancy.
  
  
  METHODS
  A systematic search in the main bibliographic databases was carried out. Three independent observers identified the odds ratios and regression coefficients that allowed for the estimation of the risk of DS after ultrasound screening. Four of the clinical prediction rules were integrated into a computer application (ecodown 2.0(®) ).
  
  
  RESULTS
  A total of ten clinical prediction rules were found. Three had been validated, two internally and one externally. We empirically checked the accuracy of the clinical prediction rule estimates obtained from 2216 ultrasound scans performed at our hospital. The application of the clinical prediction rules elaborated by Nicolaides and Zhong to the 2216 ultrasound scans showed a low concordance.
  
  
  CONCLUSIONS
  Clinical prediction rules allow for the integration of second-trimester ultrasound findings to calculate the risk of DS. However, results from the different clinical prediction rules are not concordant and may generate situations of overestimation or underestimation of the risk of DS. It is thus necessary to validate these clinical prediction rules externally to decide which is most suitable for clinical use.
authors.affiliation: Department of Obstetrics and Gynecology, Hospital General La Mancha Centro, Alcázar de San Juan, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Moreno-Cid
authors.forename: José María
authors.initials: JM
authors.lastname: Tenías Burillo
authors.forename: Ana
authors.initials: A
authors.lastname: Rubio-Lorente
authors.forename: María José
authors.initials: MJ
authors.lastname: Rodríguez
authors.forename: Gema
authors.initials: G
authors.lastname: Bueno-Pacheco
authors.forename: Carmen
authors.initials: C
authors.lastname: Román-Ortiz
authors.forename: Ángel
authors.initials: Á
authors.lastname: Arias
mesh_terms: D003661:Decision Support Techniques; D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D018570:Risk Assessment; D012984:Software; D016216:Ultrasonography, Prenatal