MEASURING QUALITY-OF-LIFE IN COSMETIC SURGERY PATIENTS WITH A CONDITION-SPECIFIC INSTRUMENT - THE DERRIFORD SCALE

Objective - To assess the reliability, validity and sensitivity to cha nge of the Derriford Scale, a quality of life instrument designed to a ssess the distress and dysfunction experienced by people who are self- conscious about their physical appearance. Subjects and design - Posta l questionnaire survey of 656 cosmetic surgery patients recruited from new referral letters and plastic surgery waiting list reports. A tota l of 443 subjects completed and returned the questionnaire. Of these r espondents, 203 were sent a second questionnaire to assess reproducibi lity, of whom 155 subjects responded. Main outcome measures - Reliabil ity was assessed in terms of internal consistency and reproducibility. Face, content and construct validity were also investigated. Results - The analyses led to mixed results. There was some evidence of intern al consistency, but a number of items had low endorsement levels and t here may be scope for reducing the overall size of the instrument. Whe n assessed for reproducibility, the level of agreement between scores of individuals completing the questionnaire on two occasions was high, but an important systematic shift in responses was also detected. Cor relations between the other health status measures and the Derriford S cale provided some evidence of construct validity. Conclusion - In its present form the Derriford Scale has good descriptive value, but ther e are some measurement problems identified in this report that need to be addressed before the scale is taken up into general use.