title: Evaluation of the impact of density gradient centrifugation on fetal cell loss during enrichment from maternal peripheral blood.
abstract: OBJECTIVE
  Physical separation by density gradient centrifugation (DGC) is usually used as an initial step of multistep enrichment protocols for purification of fetal cells (FCs) from maternal blood. Many protocols were designed but no single approach was efficient enough to provide noninvasive prenatal diagnosis. Procedures and methods were difficult to compare because of the nonuniformity of protocols among different groups. Recovery of FCs is jeopardized by their loss during the process of enrichment. Any loss of FCs must be minimized because of the multiplicative effect of each step of the enrichment process. The main objective of this study was to evaluate FC loss caused by DGC.
  
  
  METHODS
  Fetal cells were quantified in peripheral blood samples obtained from both euploid and aneuploid pregnancies before and after enrichment by buoyant DGC using Histopaque 1.119 g/mL.
  
  
  RESULTS
  Density gradient centrifugation results in major loss of 60% to 80% of rare FCs, which may further complicate subsequent enrichment procedures. Eliminating aggressive manipulations can significantly minimize FC loss.
  
  
  CONCLUSIONS
  Data obtained raise questions about the appropriateness of the DGC step for the enrichment of rare FCs and argues for the use of the alternative nonaggressive version of the procedure presented here or prioritizing other methods of enrichments.
authors.affiliation: Division of Genetics, Department of Pediatrics, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Emad
authors.forename: Régen
authors.initials: R
authors.lastname: Drouin
mesh_terms: D016022:Case-Control Studies; D002499:Centrifugation, Density Gradient; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D016014:Linear Models; D008297:Male; D062145:Maternal Serum Screening Tests / Q000379:methods*; D015999:Multivariate Analysis; D011247:Pregnancy