title: Biochemical screening for Down syndrome in pregnancies following renal transplantation.
abstract: OBJECTIVE
  To assess the performance of the double marker test [free beta-human chorionic gonadotrophin (beta-hCG) and alpha-fetoprotein (AFP)] as a screening test for Down syndrome in pregnant patients who had a prior renal transplant.
  
  
  METHODS
  A retrospective study.
  
  
  METHODS
  The Fetal Medicine Unit, Royal Free Hospital, London, UK.
  
  
  METHODS
  Detailed records of 14 post-renal transplant pregnancies were obtained from the Renal Unit of our hospital where the patients were followed up. The serum concentrations of urea, creatinine, free beta-hCG and AFP at the time of the double marker test were recorded, with a cut-off point of 1:250 for the double marker test. A control group of 14 normal pregnancies matched for age, parity and gestational age was used. The Mann-Whitney U-test and t-tests of unequal variance were applied to compare parameters of the study and the control groups.
  
  
  RESULTS
  Two patients in each group were high risk for Down syndrome and amniocentesis revealed normal karyotype. No babies with Down syndrome were delivered in either group. Regression analysis showed significant correlation between free beta-hCG and urea concentrations (p<0.001) and free beta-hCG and creatinine concentrations (p<0.001), but not for AFP.
  
  
  CONCLUSIONS
  The present study demonstrates that residual renal function alterations persisting after renal transplantation can affect the levels of free beta-hCG and AFP, thus resulting in false-positive screening for Down syndrome. First trimester nuchal translucency (NT) measurement in combination with second trimester ultrasonographic markers can be used in these patients, or alternatively the free beta-hCG levels should be corrected according to the serum creatinine levels.
authors.affiliation: Fetal Medicine Unit, The Royal Free Hospital, Pond Street, London NW3 2QG, UK.
authors.forename: C N
authors.initials: CN
authors.lastname: Karidas
authors.forename: G D
authors.initials: GD
authors.lastname: Michailidis
authors.forename: K
authors.initials: K
authors.lastname: Spencer
authors.forename: D L
authors.initials: DL
authors.lastname: Economides
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D003404:Creatinine / Q000097:blood; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D005865:Gestational Age; D006801:Humans; D016030:Kidney Transplantation; D010298:Parity; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D014508:Urea / Q000097:blood; D000509:alpha-Fetoproteins / Q000032:analysis
chemical_list: D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D000509:alpha-Fetoproteins; D014508:Urea; D003404:Creatinine