title: Validity of dietary patterns derived in nutrition surveys using a priori and a posteriori multivariate statistical methods.
abstract: OBJECTIVE
  To evaluate the validity of dietary patterns derived using both a priori and a posteriori methods.
  
  
  METHODS
  Five hundred individuals (46 ± 16 years, 40% males) completed a valid 76-food item food frequency questionnaire and a 3-day dairy. The MedDietScore was used to a priori assess the adherence to the Mediterranean diet, while principal components and cluster analysis were used as the a posteriori methods.
  
  
  RESULTS
  Both the a priori and a posteriori methods used led to relatively low-validity dietary patterns. However, the level of validity reached significance in many cases and, also, varied by the type of validation method used (i.e. Bland and Altman, non-parametric criteria, etc.).
  
  
  CONCLUSIONS
  The aforementioned findings may suggest that the use of both a priori and a posteriori pattern analysis in nutrition surveys should be made with conscious thought and further research is needed in order to establish robust methodologies to assess the validity of patterns.
authors.affiliation: Group of Biostatistics, Epidemiology and Research Methods, Department of Science of Dietetics-Nutrition, Harokopio University, Athens, Greece.
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Bountziouka
authors.forename: George
authors.initials: G
authors.lastname: Tzavelas
authors.forename: Evangelos
authors.initials: E
authors.lastname: Polychronopoulos
authors.forename: Theodore C
authors.initials: TC
authors.lastname: Constantinidis
authors.forename: Demosthenes B
authors.initials: DB
authors.lastname: Panagiotakos
mesh_terms: D000328:Adult; D016000:Cluster Analysis; D015930:Diet Records; D038441:Diet, Mediterranean; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009749:Nutrition Surveys / Q000379:methods*; D025341:Principal Component Analysis; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires