title: Second-trimester maternal serum CA-125 versus estriol in the multiple-marker screening test for Down syndrome.
abstract: OBJECTIVE
  To determine the ability of second-trimester maternal serum CA-125 levels to detect fetal Down syndrome.
  
  
  METHODS
  From stored, second-trimester maternal serum analyzed previously with the multiple-marker screening test for fetal Down syndrome, we selected 306 samples from euploid pregnancies and 22 samples from Down syndrome pregnancies at 14-20 weeks' gestation. CA-125 levels were measured by enzyme-linked immunosorbent assay and converted to gestational week-specific multiples of the median (MoM).
  
  
  RESULTS
  The mean maternal age (+/- standard deviation) of the study population was 35.5 +/- 5.3 years. The Down syndrome group CA-125 mean MoM was significantly higher than the euploid group mean MoM (1.47 +/- 0.51 MoM versus 1.05 +/- 0.44 MoM; P < .001). CA-125 at or above 1.5 MoM identified 10 of 22 (45%) Down syndrome cases. Substituting CA-125 for estriol (E3) in the multiple-marker screening test resulted in a lower screen-positive rate (67 of 328, 20% [95% confidence interval {CI} 16, 25] versus 91 of 328, 28% [95% CI 23, 33]) with a similar Down syndrome detection rate (18 of 22, 82%). Alternatively, when the screen-positive rate was held constant, the Down syndrome detection rate improved (20 of 22, 91% [95% CI 71, 99] versus 18 of 22, 82% [95% CI 60, 95]).
  
  
  CONCLUSIONS
  Down syndrome pregnancies have higher second-trimester maternal serum CA-125 levels than euploid pregnancies. CA-125 may be superior to E3 in the multiple-marker screening test for fetal Down syndrome.
authors.affiliation: Department of Obstetrics and Gynecology, University of Alabama at Birmingham, USA.
authors.forename: K D
authors.initials: KD
authors.lastname: Wenstrom
authors.forename: J
authors.initials: J
authors.lastname: Owen
authors.forename: L
authors.initials: L
authors.lastname: Boots
mesh_terms: D000328:Adult; D018394:CA-125 Antigen / Q000097:blood*; D004314:Down Syndrome / Q000175:diagnosis*; D004964:Estriol / Q000097:blood*; D005260:Female; D006801:Humans; D011247:Pregnancy / Q000097:blood*; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis
chemical_list: D018394:CA-125 Antigen; D004964:Estriol