title: Evaluation of second trimester maternal serum screening for Down's Syndrome using the Spiegelhalter-Knill-Jones (S-KJ) approach.
abstract: OBJECTIVE
  Risk estimation for Down's syndrome in antenatal serum screening with maternal age and multiple serum biomarkers is usually complicated and computationally intensive. We have developed a simple scoring system using the Spiegelhalter-Knill-Jones approach, which was based on Bayesian theorem and the logistic regression model.
  
  
  METHODS
  A prospective data set with 3842 singleton pregnancies including 6 affected pregnancies served as "trained data". Maternal age, maternal serum alpha-fetoprotein and human chorionic gonadotrophin levels of each pregnant woman were adopted as the predictors to establish the scoring model using the S-KJ approach. Model validation was undertaken using a receiver operating characteristics (ROC) curve with another 3050 singleton pregnancies including 4 affected pregnancies ("validated data").
  
  
  RESULTS
  For the trained data the sensitivity and specificity of the scoring system at cut-off value of 1:250 was 66.7% and 92.6%, respectively. For the validated data the sensitivity and specificity at the same cut-off point was 75% and 92.2%, respectively. The area under the ROC curve of the trained and validated data was 76.96% (95% CI: 51.80-100%), and 94.07% (95% CI: 84.47-100%), respectively.
  
  
  CONCLUSIONS
  The S-KJ scoring system has been demonstrated to be a simple, and efficient method for the risk estimation of Down's syndrome. This system can be applied to other antenatal serum screening systems.
authors.affiliation: Department of Obstetrics and Gynecology, National Taiwan, University Hospital, National Taiwan University, Taiwan.
authors.forename: Hsiao-Lin
authors.initials: HL
authors.lastname: Hwa
authors.forename: Ming-Fang
authors.initials: MF
authors.lastname: Yen
authors.forename: Fon-Jou
authors.initials: FJ
authors.lastname: Hsieh
authors.forename: Tsang-Ming
authors.initials: TM
authors.lastname: Ko
authors.forename: Tony Hsiu-Hsi
authors.initials: TH
authors.lastname: Chen
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D006063:Chorionic Gonadotropin / Q000097:blood; D004314:Down Syndrome / Q000097:blood* / Q000453:epidemiology; D005260:Female; D006801:Humans; D016015:Logistic Models; D008423:Maternal Age; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis / Q000379:methods*; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D013624:Taiwan / Q000453:epidemiology; D000509:alpha-Fetoproteins / Q000378:metabolism
chemical_list: D015415:Biomarkers; D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins