title: An instrument to assess quality of life in relation to nutrition: item generation, item reduction and initial validation.
abstract: BACKGROUND
  It is arguable that modification of diet, given its potential for positive health outcomes, should be widely advocated and adopted. However, food intake, as a basic human need, and its modification may be accompanied by sensations of both pleasure and despondency and may consequently affect to quality of life (QoL). Thus, the feasibility and success of dietary changes will depend, at least partly, on whether potential negative influences on QoL can be avoided. This is of particular importance in the context of dietary intervention studies and in the development of new food products to improve health and well being. Instruments to measure the impact of nutrition on quality of life in the general population, however, are few and far between. Therefore, the aim of this project was to develop an instrument for measuring QoL related to nutrition in the general population.
  
  
  RESULTS
  We recruited participants from the general population and followed standard methodology for quality of life instrument development (identification of population, item selection, n = 24; item reduction, n = 81; item presentation, n = 12; pretesting of questionnaire and initial validation, n = 2576; construct validation n = 128; and test-retest reliability n = 20). Of 187 initial items, 29 were selected for final presentation. Factor analysis revealed an instrument with 5 domains. The instrument demonstrated good cross-sectional divergent and convergent construct validity when correlated with scores of the 8 domains of the SF-36 (ranging from -0.078 to 0.562, 19 out of 40 tested correlations were statistically significant and 24 correlations were predicted correctly) and good test-retest reliability (intra-class correlation coefficients from 0.71 for symptoms to 0.90).
  
  
  CONCLUSIONS
  We developed and validated an instrument with 29 items across 5 domains to assess quality of life related to nutrition and other aspects of food intake. The instrument demonstrated good face and construct validity as well as good reliability. Future work will focus on the evaluation of longitudinal construct validity and responsiveness.
authors.affiliation: Department of Medicine, University at Buffalo, State University of New York, Buffalo, New York, USA. schuneh@mcmaster.ca
authors.forename: Holger J
authors.initials: HJ
authors.lastname: Schünemann
authors.forename: Francesca
authors.initials: F
authors.lastname: Sperati
authors.forename: Maddalena
authors.initials: M
authors.lastname: Barba
authors.forename: Nancy
authors.initials: N
authors.lastname: Santesso
authors.forename: Camilla
authors.initials: C
authors.lastname: Melegari
authors.forename: Elie A
authors.initials: EA
authors.lastname: Akl
authors.forename: Gordon
authors.initials: G
authors.lastname: Guyatt
authors.forename: Paola
authors.initials: P
authors.lastname: Muti
mesh_terms: D000328:Adult; D000368:Aged; D001835:Body Weight; D004435:Eating / Q000523:psychology*; D005260:Female; D006801:Humans; D008019:Life Style; D008297:Male; D009752:Nutritional Status; D057181:Pleasure; D011594:Psychometrics; D011788:Quality of Life / Q000523:psychology*; D019057:Quality-Adjusted Life Years; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires / Q000592:standards*