title: Application and interpretation of multiple statistical tests to evaluate validity of dietary intake assessment methods.
abstract: BACKGROUND
  Several statistical tests are currently applied to evaluate validity of dietary intake assessment methods. However, they provide information on different facets of validity. There is also no consensus on types and combinations of tests that should be applied to reflect acceptable validity for intakes. We aimed to 1) conduct a review to identify the tests and interpretation criteria used where dietary assessment methods was validated against a reference method and 2) illustrate the value of and challenges that arise in interpretation of outcomes of multiple statistical tests in assessment of validity using a test data set.
  
  
  METHODS
  An in-depth literature review was undertaken to identify the range of statistical tests used in the validation of quantitative food frequency questionnaires (QFFQs). Four databases were accessed to search for statistical methods and interpretation criteria used in papers focusing on relative validity. The identified tests and interpretation criteria were applied to a data set obtained using a QFFQ and four repeated 24-hour recalls from 47 adults (18-65 years) residing in rural Eastern Cape, South Africa.
  
  
  RESULTS
  102 studies were screened and 60 were included. Six statistical tests were identified; five with one set of interpretation criteria and one with two sets of criteria, resulting in seven possible validity interpretation outcomes. Twenty-one different combinations of these tests were identified, with the majority including three or less tests. Coefficient of correlation was the most commonly used (as a single test or in combination with one or more tests). Results of our application and interpretation of multiple statistical tests to assess validity of energy, macronutrients and selected micronutrients estimates illustrate that for most of the nutrients considered, some outcomes support validity, while others do not.
  
  
  CONCLUSIONS
  One to three statistical tests may not be sufficient to provide comprehensive insights into various facets of validity. Results of our application and interpretation of multiple statistical tests support the value of such an approach in gaining comprehensive insights in different facets of validity. These insights should be considered in the formulation of conclusions regarding validity to answer a particular dietary intake related research question.
authors.affiliation: Centre of Excellence for Nutrition (CEN), North-West University, Private Bag X6001, Nutrition, Box 594, Potchefstroom, 2520, South Africa. tani.lombard@nwu.ac.za.
authors.forename: Martani J
authors.initials: MJ
authors.lastname: Lombard
authors.affiliation: Division of Human Nutrition, University of Cape Town, Cape Town, South Africa. nelia.steyn@uct.ac.za.
authors.forename: Nelia P
authors.initials: NP
authors.lastname: Steyn
authors.affiliation: School of Medicine, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, Australia. karenc@uow.edu.au.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Charlton
authors.affiliation: Division of Human Nutrition, University of Cape Town, Cape Town, South Africa. marjanne.senekal@uct.ac.za.
authors.forename: Marjanne
authors.initials: M
authors.lastname: Senekal
mesh_terms: D016208:Databases, Factual; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D002149:Energy Intake; D005247:Feeding Behavior; D005492:Folic Acid / Q000008:administration & dosage; D006801:Humans; D019266:Iron, Dietary / Q000008:administration & dosage; D011939:Mental Recall; D018977:Micronutrients / Q000008:administration & dosage; D015596:Nutrition Assessment; D015203:Reproducibility of Results; D012424:Rural Population; D013019:South Africa; D011795:Surveys and Questionnaires; D014801:Vitamin A / Q000008:administration & dosage
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D019266:Iron, Dietary; D018977:Micronutrients; D014801:Vitamin A; D005492:Folic Acid