Validity of an instrument assessing oral health problems in people with Down syndrome

The aim of this study was to validate a proxy measure of oral health designed to be completed by the English-speaking parents of people with Down syndrome (DS) aged four years or more.

Items were generated through literature review, interviews with parents of people with DS and professional experts and through frequency testing. Data were gathered from one population-based and two clinic-based samples for the separate aspects of validation. Validation consisted of evaluation of: i) internal reliability of the domain structure through Cronbach's alpha; ii) criterion validity against clinical indicators and a clinician's evaluation of some items; iii) construct validity involving an age-matched comparison of domain scores between people with DS and non-DS siblings, and within the DS group by health status indicators; and iv) test-retest reliability through the generation of intra-class correlation coefficients (ICC).

A 20-item instrument with four domains (communication, eating, parafunction and symptoms) was developed. Cronbach's alpha by domain was 0.5-0.8. Indicators of criterion validity for domains against clinical indicators (Spearman's coefficient 0.1-0.4) and parent-rated items against clinician-rated items (weighted Kappa 0.1-0.8) were varied as anticipated. Indicators of construct validity (differences with non-DS siblings and correlations with medical status within the DS group) were excellent. Test-retest reliability was good (ICC range 0.64-0.84).

These data suggest the test instrument is valid as a descriptive, discriminative, proxy English language measure of oral health problems in people with DS aged four years or more.