Assessment of a condition-specific quality-of-life measure for patients with developmentally absent teeth: validity and reliability testing.

OBJECTIVES: This article describes the process of validity and reliability testing of a condition-specific quality-of-life measure for patients with hypodontia presenting for orthodontic treatment. The development of the instrument is described in a previous article.

SETTING AND SAMPLE POPULATION: Royal Devon and Exeter NHS Foundation Trust & Musgrove Park Hospital, Taunton.

MATERIALS AND METHODS: The child perception questionnaire was used as a standard against which to test criterion validity. The Bland and Altman method was used to check agreement between the two questionnaires. Construct validity was tested using principal component analysis on the four sections of the questionnaire. Test-retest reliability was tested using intraclass correlation coefficient and Bland and Altman method. Cronbach's alpha was used to test internal consistency reliability.

RESULTS: Overall the questionnaire showed good reliability, criterion and construct validity. This together with previous evidence of good face and content validity suggests that the instrument may prove useful in clinical practice and further research.

CONCLUSIONS: This study has demonstrated that the newly developed condition-specific quality-of-life questionnaire is both valid and reliable for use in young patients with hypodontia.