title: Triple test screening for Down syndrome: an Egyptian-tailored study.
abstract: BACKGROUND
  The incidence of Down syndrome (DS) in Egypt varies between 1:555 and 1:770 and its screening by triple test is becoming increasingly popular nowadays. Results, however, seem inaccurate due to the lack of Egyptian-specific information needed for risk calculation and a clear policy for programme implementation. Our study aimed at calculation and validation of the triple marker medians used in screening Egyptian females as well as to recommend programme conventions to unify screening in this country.
  
  
  METHODS
  The study was conducted on 668 Egyptian women, in weeks 15-20 of pregnancy as proven by sonar. Chorionic gonadotropin (CG), α-fetoprotein (AFP) and unconjugated oestriol (uE3) were measured on Siemens Immulite analyzer. Medians of the three parameters were calculated, regressed against gestational age (GA) and weighted by the number of participants/week. Equations were derived to adjust each parameter to the maternal weight and were centered on the median Egyptian weight. Prisca software was fed with the above data, multiples-of-median (MoM) and DS risks were calculated and the screening performance was evaluated at a mid-trimester risk cutoff of 1:270.
  
  
  RESULTS
  Log-linear [AFP/uE3 = 10(A+B*GA)] and exponential equations [CG = A*e (B*GA)] were derived and the regressed medians were found to follow similar patterns to other Asian and Western medians. Oestriol was always lowest (even halved) while CG and AFP were intermediate. A linear reciprocal model best fitted weight distribution among Egyptians and successfully adjusted each parameter to a weight of 78.2 kg. Epidemiological monitoring of these recommendations revealed satisfactory performance in terms of 6.7% initial positive rate and 1.00 grand MoM.
  
  
  CONCLUSIONS
  Adoption of the above recommendations is hoped to pave the way to a successful DS screening programme tailored to Egyptian peculiarities.
authors.affiliation: Clinical and Chemical Pathology Department, Faculty of Medicine, Cairo University, Cairo, Egypt.
authors.forename: Hazem S
authors.initials: HS
authors.lastname: Abou-Youssef
authors.affiliation: Clinical and Chemical Pathology Department, Faculty of Medicine, Cairo University, Cairo, Egypt.
authors.forename: Manal M
authors.initials: MM
authors.lastname: Kamal
authors.affiliation: Clinical and Chemical Pathology Department, Faculty of Medicine, Cairo University, Cairo, Egypt.
authors.forename: Dina A
authors.initials: DA
authors.lastname: Mehaney
mesh_terms: D000328:Adult; D006063:Chorionic Gonadotropin / Q000097:blood; D004314:Down Syndrome / Q000175:diagnosis*; D004534:Egypt; D004964:Estriol / Q000097:blood; D005260:Female; D006801:Humans; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D012044:Regression Analysis; D000509:alpha-Fetoproteins / Q000032:analysis
chemical_list: D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins; D004964:Estriol