title: Reproducibility of telomere length assessment: an international collaborative study.
abstract: BACKGROUND
  Telomere length is a putative biomarker of ageing, morbidity and mortality. Its application is hampered by lack of widely applicable reference ranges and uncertainty regarding the present limits of measurement reproducibility within and between laboratories.
  
  
  METHODS
  We instigated an international collaborative study of telomere length assessment: 10 different laboratories, employing 3 different techniques [Southern blotting, single telomere length analysis (STELA) and real-time quantitative PCR (qPCR)] performed two rounds of fully blinded measurements on 10 human DNA samples per round to enable unbiased assessment of intra- and inter-batch variation between laboratories and techniques.
  
  
  RESULTS
  Absolute results from different laboratories differed widely and could thus not be compared directly, but rankings of relative telomere lengths were highly correlated (correlation coefficients of 0.63-0.99). Intra-technique correlations were similar for Southern blotting and qPCR and were stronger than inter-technique ones. However, inter-laboratory coefficients of variation (CVs) averaged about 10% for Southern blotting and STELA and more than 20% for qPCR. This difference was compensated for by a higher dynamic range for the qPCR method as shown by equal variance after z-scoring. Technical variation per laboratory, measured as median of intra- and inter-batch CVs, ranged from 1.4% to 9.5%, with differences between laboratories only marginally significant (P = 0.06). Gel-based and PCR-based techniques were not different in accuracy.
  
  
  CONCLUSIONS
  Intra- and inter-laboratory technical variation severely limits the usefulness of data pooling and excludes sharing of reference ranges between laboratories. We propose to establish a common set of physical telomere length standards to improve comparability of telomere length estimates between laboratories.
authors.affiliation: Newcastle University Institute for Ageing, Newcastle University, Newcastle, UK.
authors.forename: Carmen M
authors.initials: CM
authors.lastname: Martin-Ruiz
authors.affiliation: Institute of Cancer and Genetics, Cardiff University, Cardiff, UK.
authors.forename: Duncan
authors.initials: D
authors.lastname: Baird
authors.affiliation: Institute of Cancer and Genetics, Cardiff University, Cardiff, UK.
authors.forename: Laureline
authors.initials: L
authors.lastname: Roger
authors.affiliation: Deutsches Krebsforschungszentrum (DKFZ), Heidelberg, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Boukamp
authors.affiliation: Deutsches Krebsforschungszentrum (DKFZ), Heidelberg, Germany.
authors.forename: Damir
authors.initials: D
authors.lastname: Krunic
authors.affiliation: Department of Human Genetics, University of Utah, Salt Lake City, UT, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Cawthon
authors.affiliation: Department of Cardiology, University of Groningen, Groningen, The Netherlands.
authors.forename: Martin M
authors.initials: MM
authors.lastname: Dokter
authors.affiliation: Department of Cardiology, University of Groningen, Groningen, The Netherlands.
authors.forename: Pim
authors.initials: P
authors.lastname: van der Harst
authors.affiliation: Bimetra, Clinical Research Center, Ghent University Hospital, Ghent, Belgium.
authors.forename: Sofie
authors.initials: S
authors.lastname: Bekaert
authors.affiliation: Department of Mathematical Modelling, Statistics and Bioinformatics, Ghent University, Ghent, Belgium.
authors.forename: Tim
authors.initials: T
authors.lastname: de Meyer
authors.affiliation: Department of Medical Biosciences, Umeå University, Umeå, Sweden.
authors.forename: Goran
authors.initials: G
authors.lastname: Roos
authors.affiliation: Department of Medical Biosciences, Umeå University, Umeå, Sweden.
authors.forename: Ulrika
authors.initials: U
authors.lastname: Svenson
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Leicester, UK.
authors.forename: Veryan
authors.initials: V
authors.lastname: Codd
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Leicester, UK.
authors.forename: Nilesh J
authors.initials: NJ
authors.lastname: Samani
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, Glasgow, UK.
authors.forename: Liane
authors.initials: L
authors.lastname: McGlynn
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, Glasgow, UK.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Shiels
authors.affiliation: Department of Public Health and Primary Care.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Pooley
authors.affiliation: Department of Oncology, Centre for Cancer Genetic Epidemiology, University of Cambridge, Cambridge, UK and.
authors.forename: Alison M
authors.initials: AM
authors.lastname: Dunning
authors.affiliation: MRC Unit for Lifelong Health and Ageing at UCL, London, UK.
authors.forename: Rachel
authors.initials: R
authors.lastname: Cooper
authors.affiliation: MRC Unit for Lifelong Health and Ageing at UCL, London, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Wong
authors.affiliation: Newcastle University Institute for Ageing, Newcastle University, Newcastle, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kingston
authors.affiliation: Newcastle University Institute for Ageing, Newcastle University, Newcastle, UK, t.vonzglinicki@newcastle.ac.uk.
authors.forename: Thomas
authors.initials: T
authors.lastname: von Zglinicki
mesh_terms: D000375:Aging / Q000235:genetics*; D015415:Biomarkers; D015139:Blotting, Southern; D004247:DNA / Q000235:genetics*; D006801:Humans; D007391:International Cooperation; D060888:Real-Time Polymerase Chain Reaction; D015203:Reproducibility of Results; D016615:Telomere / Q000235:genetics*
chemical_list: D015415:Biomarkers; D004247:DNA
keywords: Ageing; biomarker; human; telomeres; variation