title: Second worldwide proficiency study on variable number of tandem repeats typing of Mycobacterium tuberculosis complex.
abstract: BACKGROUND
  The quality of variable number of tandem repeats (VNTR) typing of Mycobacterium tuberculosis was first investigated in 2009 in 37 laboratories worldwide. The results revealed an inter- and intra-laboratory reproducibility of respectively 60% and 72%. These data spurred an improvement in laboratory-specific assays and global standardisation of VNTR typing.
  
  
  OBJECTIVE
  To measure the effects of the technical improvements and increased standardisation, a test panel consisting of 30 M. tuberculosis complex DNA samples was distributed for VNTR typing in 41 participating laboratories from 36 countries.
  
  
  RESULTS
  The inter- and intra-laboratory reproducibility increased overall to respectively 78% and 88%. The 33 laboratories that participated in both the first and second proficiency studies improved their inter- and intra-laboratory reproducibility from 62% and 72% to respectively 79% and 88%. The largest improvement in reproducibility was detected in 10 laboratories that use an in-house polymerase chain reaction technique and perform amplicon sizing using gel electrophoresis. Detailed error analysis revealed a reduction in the number of systematic errors, sample exchange events and non-amplifiable loci.
  
  
  CONCLUSIONS
  This second worldwide proficiency study indicates a substantial increase in the reproducibility of VNTR typing of M. tuberculosis. This will contribute to a more meaningful interpretation of molecular epidemiological and phylogenetic studies on the M. tuberculosis complex.
authors.affiliation: National Tuberculosis Reference Laboratory, Center for Infectious Diseases Research, Diagnostics and Screening, Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: J L
authors.initials: JL
authors.lastname: de Beer
authors.affiliation: European Centre for Disease Prevention and Control, Stockholm, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Ködmön
authors.affiliation: Department of Medical Microbiology, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: van Ingen
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Lille, France.
authors.forename: P
authors.initials: P
authors.lastname: Supply
authors.affiliation: National Tuberculosis Reference Laboratory, Center for Infectious Diseases Research, Diagnostics and Screening, Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: van Soolingen
mesh_terms: D015373:Bacterial Typing Techniques / Q000592:standards*; D004269:DNA, Bacterial / Q000235:genetics*; D004587:Electrophoresis, Agar Gel / Q000592:standards; D006801:Humans; D059021:Laboratory Proficiency Testing / Q000592:standards*; D018598:Minisatellite Repeats; D009169:Mycobacterium tuberculosis / Q000145:classification / Q000235:genetics*; D015588:Observer Variation; D016133:Polymerase Chain Reaction / Q000592:standards; D011237:Predictive Value of Tests; D019984:Quality Indicators, Health Care / Q000592:standards; D015203:Reproducibility of Results
chemical_list: D004269:DNA, Bacterial