title: Platelet contamination causes large variation as well as overestimation of mitochondrial DNA content of peripheral blood mononuclear cells.
abstract: BACKGROUND
  Alterations in the copy number of mitochondrial DNA (mtDNA) play a role in the pathogenesis of mitochondrial diseases and other many common diseases. Recently, the copy number of leukocyte mtDNA has been considered to serve as a biomarker to monitor or chase such diseases. Therefore, reproducible mtDNA measurement is required.
  
  
  METHODS
  Peripheral blood mononuclear cells were prepared by a density-based method. The mtDNA/cell was measured by quantitative realtime polymerase chain reaction.
  
  
  RESULTS
  The degree of platelet contamination varied to a large extent among preparations. The mtDNA copy numbers per mononuclear cell were 269 +/- 51 and 146 +/- 14 in the samples before and after the platelet depletion, respectively.
  
  
  CONCLUSIONS
  A density-based mononuclear cell preparation causes heavy platelet contamination. The platelet depletion from a sample is particularly important for comparing the mtDNA contents between different dates or between different patients.
authors.affiliation: Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Graduate School of Medical Sciences, 3-1-1 Maidashi Higashi-ku, Fukuoka, Japan.
authors.forename: Michiyo
authors.initials: M
authors.lastname: Urata
authors.forename: Yui
authors.initials: Y
authors.lastname: Koga-Wada
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Kayamori
authors.forename: Dongchon
authors.initials: D
authors.lastname: Kang