title: The reliability of two methods of utility assessment in dentistry.
abstract: OBJECTIVE
  The objective of this study was to investigate the modification of two utility assessment techniques (visual analogue scale and daily time trade-off) used in medicine to the dental setting, with a focus on their test-retest reliability and ease of use.
  
  
  METHODS
  The study involved a postal questionnaire survey which incorporated a dental visual analogue scale (DVAS) to assess utility values for 12 specified tooth states, and a specifically designed instrument, the dental freetime trade-off (DFTO) to assess utility of the participants' current dental health state.
  
  
  METHODS
  A total of 582 regularly attending adolescent dental patients were sent the questionnaire. A further 100 of those who fully completed the relevant sections of the questionnaire were sent a repeat questionnaire to facilitate assessment of test-retest reliability.
  
  
  RESULTS
  A final response rate of 74.7% was achieved with the mean age of respondents being 17 years. Fifty per cent of those sent a repeat questionnaire for the purposes of reliability assessment returned the questionnaire. Test-retest reliability of both utility assessment techniques appeared acceptable. Spearman correlation coefficients for the dental freetime trade-off (DFTO) and the dental visual analogue scale (DVAS) were (0.67 and 0.83 respectively. Promising results, in terms of utility values, were elicited from the DVAS whilst utility values elicited using the DFTO were highly skewed.
  
  
  CONCLUSIONS
  The newly developed modification to the daily time trade-off technique, the DFTO, showed a good level of test-retest reliability and ease of completion although the highly skewed utility results produced may indicate a design flaw. The DVAS however, appears to show promise, in terms of test-retest reliability, ease of completion and resultant utility values.
authors.affiliation: Dental Health Services Research Unit, Dental Hospital and School, Dundee, UK.
authors.forename: H E
authors.initials: HE
authors.lastname: Fyffe
authors.forename: C
authors.initials: C
authors.lastname: Deery
authors.forename: Z
authors.initials: Z
authors.lastname: Nugent
authors.forename: N M
authors.initials: NM
authors.lastname: Nuttall
authors.forename: N B
authors.initials: NB
authors.lastname: Pitts
mesh_terms: D000293:Adolescent; D001294:Attitude to Health; D003729:Dental Care / Q000523:psychology / Q000706:statistics & numerical data*; D006801:Humans; D009909:Oral Health; D011446:Prospective Studies; D015203:Reproducibility of Results; D012606:Scotland; D011795:Surveys and Questionnaires; D013997:Time Factors; D014600:Utilization Review / Q000379:methods* / Q000706:statistics & numerical data