title: The analysis of one or two blastomeres for PGD using fluorescence in-situ hybridization.
abstract: BACKGROUND
  The analysis of one or two blastomeres for PGD using fluorescence in-situ hybridization (FISH) is debated. The proportion of analysable embryos, false negatives, false positives, sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV) and efficiency were evaluated when one or two blastomeres were analysed.
  
  
  METHODS
  Embryos of patients having PGD for aneuploidy screening were assigned non-randomly to two groups: group I (n = 413), more slow cleaving embryos with one nucleus for analysis, and group II (n = 1366), regularly cleaving embryos with two nuclei for analysis. A two-round FISH procedure was performed investigating seven chromosomes; 486 embryos were reanalysed.
  
  
  RESULTS
  The proportion of analysable embryos was significantly higher in group II (98.2 versus 95.9%) (P = 0.04). Despite the apparently increased false-positive rate (group I: 25.6% and group II: 13.6%) and the decreased PPV (group I: 91.9% and group II: 96.7%), specificity (group I: 74.4% and group II: 86.4%) and efficiency (group I: 93.5% and group II: 97.3%) in group I, no significance was reached (P = 0.11, P = 0.053, P = 0.11 and P = 0.06, respectively).
  
  
  CONCLUSIONS
  Although the analysis of one blastomere generates statistically significantly fewer embryos with a diagnosis than does the analysis of two blastomeres, the 2% difference may not be clinically relevant. The diagnostic accuracy is not significantly different between the two groups, hence not favouring the analysis of one or two blastomeres.
authors.affiliation: Centre for Medical Genetics, Vrije Universiteit Brussel, Belgium. an.michiels@az.vub.ac.be
authors.forename: An
authors.initials: A
authors.lastname: Michiels
authors.forename: Elvire
authors.initials: E
authors.lastname: Van Assche
authors.forename: Inge
authors.initials: I
authors.lastname: Liebaers
authors.forename: André
authors.initials: A
authors.lastname: Van Steirteghem
authors.forename: Catherine
authors.initials: C
authors.lastname: Staessen
mesh_terms: D000782:Aneuploidy; D001706:Biopsy; D001755:Blastocyst / Q000378:metabolism; D001757:Blastomeres / Q000378:metabolism*; D002877:Chromosomes, Human / Q000648:ultrastructure; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D009693:Nucleic Acid Hybridization; D011237:Predictive Value of Tests; D011247:Pregnancy; D019836:Preimplantation Diagnosis / Q000295:instrumentation* / Q000379:methods*; D012680:Sensitivity and Specificity