title: Design and implementation of the Healthy Lifestyle in Europe by Nutrition in Adolescence Cross-Sectional Study.
abstract: OBJECTIVE
  To provide an overview of the Healthy Lifestyle in Europe by Nutrition in Adolescence Cross-Sectional Study (HELENA-CSS) design, with particular attention to its quality control procedures. Other important methodological aspects are described in detail throughout this supplement.
  
  
  METHODS
  Description of the HELENA-CSS sampling and recruitment approaches, standardization and harmonization processes, data collection and analysis strategies and quality control activities.
  
  
  RESULTS
  The HELENA-CSS is a multi-centre collaborative study conducted in European adolescents located in urban settings. The data management systems, quality assurance monitoring activities, standardized manuals of operating procedures and training and study management are addressed in this paper. Various quality controls to ensure collection of valid and reliable data will be discussed in this supplement, as well as quantitative estimates of measurement error.
  
  
  CONCLUSIONS
  The great advantage of the HELENA-CSS is the strict standardization of the fieldwork and the blood analyses, which precludes to a great extent the kind of immeasurable confounding bias that often interferes when comparing results from isolated studies.
authors.affiliation: Escuela Universitaria de Ciencias de la Salud, Universidad de Zaragoza, Zaragoza, Spain. lmoreno@unizar.es
authors.forename: L A
authors.initials: LA
authors.lastname: Moreno
authors.forename: S
authors.initials: S
authors.lastname: De Henauw
authors.forename: M
authors.initials: M
authors.lastname: González-Gross
authors.forename: M
authors.initials: M
authors.lastname: Kersting
authors.forename: D
authors.initials: D
authors.lastname: Molnár
authors.forename: F
authors.initials: F
authors.lastname: Gottrand
authors.forename: L
authors.initials: L
authors.lastname: Barrios
authors.forename: M
authors.initials: M
authors.lastname: Sjöström
authors.forename: Y
authors.initials: Y
authors.lastname: Manios
authors.forename: C C
authors.initials: CC
authors.lastname: Gilbert
authors.forename: C
authors.initials: C
authors.lastname: Leclercq
authors.forename: K
authors.initials: K
authors.lastname: Widhalm
authors.forename: A
authors.initials: A
authors.lastname: Kafatos
authors.forename: A
authors.initials: A
authors.lastname: Marcos
mesh_terms: D000293:Adolescent; D003430:Cross-Sectional Studies; D003625:Data Collection; D005060:Europe; D005260:Female; D006293:Health Promotion / Q000458:organization & administration*; D006801:Humans; D008297:Male; D015337:Multicenter Studies as Topic / Q000379:methods*; D009765:Obesity / Q000517:prevention & control*; D018579:Patient Selection; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D012107:Research Design; D018401:Sample Size