Development of a condition-specific quality of life measure for patients with dentofacial deformity. I. Reliability of the instrument

The assessment of quality of life is becoming increasingly important in cli nical research. Its importance in dentistry has been realised only relative ly recently Health-related quality of life is concerned with the aspects of quality of life that relate specifically to an individual's health. This m ay be measured using two groups of instruments: (i) generic measures, which provide a summary of health-related quality of life and sometimes generate a single index measure of health or (ii) condition-specific measures, whic h focus on a particular condition, disease, population or problem and are p otentially more responsive to small, but clinically important, changes in h ealth. Objectives: The aim of this study was to develop a condition-specifi c quality of life measure for those patients with severe dentofacial deform ity who were requesting orthognathic treatment and to assess the reliabilit y of this instrument. Method: Instrument content was derived through a lite rature review and interviews with clinicians and patients. The resulting in strument was tested for internal consistency and test-retest reliability. R esults and conclusions: The instrument was found to divide into four clinic ally meaningful domains. Internal consistency and test-retest reliability w ere good. Patient acceptance of the questionnaire was also encouraging.